Nim/lib/pure/strutils.nim

#
#
#            Nim's Runtime Library
#        (c) Copyright 2012 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module contains various string utility routines.
## See the module `re <re.html>`_ for regular expression support.
## See the module `pegs <pegs.html>`_ for PEG support.
## This module is available for the `JavaScript target
## <backends.html#the-javascript-target>`_.

import parseutils
from math import pow, floor, log10
from algorithm import reverse

when defined(nimVmExportFixed):
  from unicode import toLower, toUpper
  export toLower, toUpper

{.deadCodeElim: on.}  # dce option deprecated

{.push debugger:off .} # the user does not want to trace a part
                       # of the standard library!

include "system/inclrtl"

{.pop.}

# Support old split with set[char]
when defined(nimOldSplit):
  {.pragma: deprecatedSplit, deprecated.}
else:
  {.pragma: deprecatedSplit.}

const
  Whitespace* = {' ', '\t', '\v', '\r', '\l', '\f'}
    ## All the characters that count as whitespace.

  Letters* = {'A'..'Z', 'a'..'z'}
    ## the set of letters

  Digits* = {'0'..'9'}
    ## the set of digits

  HexDigits* = {'0'..'9', 'A'..'F', 'a'..'f'}
    ## the set of hexadecimal digits

  IdentChars* = {'a'..'z', 'A'..'Z', '0'..'9', '_'}
    ## the set of characters an identifier can consist of

  IdentStartChars* = {'a'..'z', 'A'..'Z', '_'}
    ## the set of characters an identifier can start with

  NewLines* = {'\13', '\10'}
    ## the set of characters a newline terminator can start with

  AllChars* = {'\x00'..'\xFF'}
    ## A set with all the possible characters.
    ##
    ## Not very useful by its own, you can use it to create *inverted* sets to
    ## make the `find() proc <#find,string,set[char],int>`_ find **invalid**
    ## characters in strings.  Example:
    ##
    ## .. code-block:: nim
    ##   let invalid = AllChars - Digits
    ##   doAssert "01234".find(invalid) == -1
    ##   doAssert "01A34".find(invalid) == 2

proc isAlphaAscii*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaAsciiChar".}=
  ## Checks whether or not `c` is alphabetical.
  ##
  ## This checks a-z, A-Z ASCII characters only.
  runnableExamples:
    doAssert isAlphaAscii('e') == true
    doAssert isAlphaAscii('E') == true
    doAssert isAlphaAscii('8') == false
  return c in Letters

proc isAlphaNumeric*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaNumericChar".} =
  ## Checks whether or not `c` is alphanumeric.
  ##
  ## This checks a-z, A-Z, 0-9 ASCII characters only.
  runnableExamples:
    doAssert isAlphaNumeric('n') == true
    doAssert isAlphaNumeric('8') == true
    doAssert isAlphaNumeric(' ') == false
  return c in Letters+Digits

proc isDigit*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsDigitChar".} =
  ## Checks whether or not `c` is a number.
  ##
  ## This checks 0-9 ASCII characters only.
  runnableExamples:
    doAssert isDigit('n') == false
    doAssert isDigit('8') == true
  return c in Digits

proc isSpaceAscii*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsSpaceAsciiChar".} =
  ## Checks whether or not `c` is a whitespace character.
  runnableExamples:
    doAssert isSpaceAscii('n') == false
    doAssert isSpaceAscii(' ') == true
  return c in Whitespace

proc isLowerAscii*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsLowerAsciiChar".} =
  ## Checks whether or not `c` is a lower case character.
  ##
  ## This checks ASCII characters only.
  runnableExamples:
    doAssert isLowerAscii('e') == true
    doAssert isLowerAscii('E') == false
    doAssert isLowerAscii('7') == false
  return c in {'a'..'z'}

proc isUpperAscii*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsUpperAsciiChar".} =
  ## Checks whether or not `c` is an upper case character.
  ##
  ## This checks ASCII characters only.
  runnableExamples:
    doAssert isUpperAscii('e') == false
    doAssert isUpperAscii('E') == true
    doAssert isUpperAscii('7') == false
  return c in {'A'..'Z'}

template isImpl(call) =
  if s.len == 0: return false
  result = true
  for c in s:
    if not call(c): return false

proc isAlphaAscii*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaAsciiStr",
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether or not `s` is alphabetical.
  ##
  ## This checks a-z, A-Z ASCII characters only.
  ## Returns true if all characters in `s` are
  ## alphabetic and there is at least one character
  ## in `s`.
  runnableExamples:
    doAssert isAlphaAscii("fooBar") == true
    doAssert isAlphaAscii("fooBar1") == false 
    doAssert isAlphaAscii("foo Bar") == false 
  isImpl isAlphaAscii

proc isAlphaNumeric*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaNumericStr",
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether or not `s` is alphanumeric.
  ##
  ## This checks a-z, A-Z, 0-9 ASCII characters only.
  ## Returns true if all characters in `s` are
  ## alpanumeric and there is at least one character
  ## in `s`.
  runnableExamples:
    doAssert isAlphaNumeric("fooBar") == true
    doAssert isAlphaNumeric("fooBar") == true 
    doAssert isAlphaNumeric("foo Bar") == false
  isImpl isAlphaNumeric

proc isDigit*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsDigitStr",
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether or not `s` is a numeric value.
  ##
  ## This checks 0-9 ASCII characters only.
  ## Returns true if all characters in `s` are
  ## numeric and there is at least one character
  ## in `s`.
  runnableExamples:
    doAssert isDigit("1908") == true
    doAssert isDigit("fooBar1") == false 
  isImpl isDigit

proc isSpaceAscii*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsSpaceAsciiStr",
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether or not `s` is completely whitespace.
  ##
  ## Returns true if all characters in `s` are whitespace
  ## characters and there is at least one character in `s`.
  runnableExamples:
    doAssert isSpaceAscii("   ") == true
    doAssert isSpaceAscii("") == false 
  isImpl isSpaceAscii

template isCaseImpl(s, charProc, skipNonAlpha) =
  var hasAtleastOneAlphaChar = false
  if s.len == 0: return false
  for c in s:
    if skipNonAlpha:
      var charIsAlpha = c.isAlphaAscii()
      if not hasAtleastOneAlphaChar:
        hasAtleastOneAlphaChar = charIsAlpha
      if charIsAlpha and (not charProc(c)):
        return false
    else:
      if not charProc(c):
        return false
  return if skipNonAlpha: hasAtleastOneAlphaChar else: true

proc isLowerAscii*(s: string, skipNonAlpha: bool): bool {.
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether ``s`` is lower case.
  ##
  ## This checks ASCII characters only.
  ##
  ## If ``skipNonAlpha`` is true, returns true if all alphabetical
  ## characters in ``s`` are lower case.  Returns false if none of the
  ## characters in ``s`` are alphabetical.
  ##
  ## If ``skipNonAlpha`` is false, returns true only if all characters
  ## in ``s`` are alphabetical and lower case.
  ##
  ## For either value of ``skipNonAlpha``, returns false if ``s`` is
  ## an empty string.
  runnableExamples:
    doAssert isLowerAscii("1foobar", false) == false
    doAssert isLowerAscii("1foobar", true) == true
    doAssert isLowerAscii("1fooBar", true) == false
  isCaseImpl(s, isLowerAscii, skipNonAlpha)

proc isUpperAscii*(s: string, skipNonAlpha: bool): bool {.
  deprecated: "Deprecated since version 0.20 since its semantics are unclear".} =
  ## Checks whether ``s`` is upper case.
  ##
  ## This checks ASCII characters only.
  ##
  ## If ``skipNonAlpha`` is true, returns true if all alphabetical
  ## characters in ``s`` are upper case.  Returns false if none of the
  ## characters in ``s`` are alphabetical.
  ##
  ## If ``skipNonAlpha`` is false, returns true only if all characters
  ## in ``s`` are alphabetical and upper case.
  ##
  ## For either value of ``skipNonAlpha``, returns false if ``s`` is
  ## an empty string.
  runnableExamples:
    doAssert isUpperAscii("1FOO", false) == false
    doAssert isUpperAscii("1FOO", true) == true
    doAssert isUpperAscii("1Foo", true) == false
  isCaseImpl(s, isUpperAscii, skipNonAlpha)

proc toLowerAscii*(c: char): char {.noSideEffect, procvar,
  rtl, extern: "nsuToLowerAsciiChar".} =
  ## Returns the lower case version of ``c``.
  ##
  ## This works only for the letters ``A-Z``. See `unicode.toLower
  ## <unicode.html#toLower>`_ for a version that works for any Unicode
  ## character.
  runnableExamples:
    doAssert toLowerAscii('A') == 'a'
    doAssert toLowerAscii('e') == 'e'
  if c in {'A'..'Z'}:
    result = chr(ord(c) + (ord('a') - ord('A')))
  else:
    result = c

template toImpl(call) =
  result = newString(len(s))
  for i in 0..len(s) - 1:
    result[i] = call(s[i])

proc toLowerAscii*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuToLowerAsciiStr".} =
  ## Converts `s` into lower case.
  ##
  ## This works only for the letters ``A-Z``. See `unicode.toLower
  ## <unicode.html#toLower>`_ for a version that works for any Unicode
  ## character.
  runnableExamples:
    doAssert toLowerAscii("FooBar!") == "foobar!"
  toImpl toLowerAscii

proc toUpperAscii*(c: char): char {.noSideEffect, procvar,
  rtl, extern: "nsuToUpperAsciiChar".} =
  ## Converts `c` into upper case.
  ##
  ## This works only for the letters ``A-Z``.  See `unicode.toUpper
  ## <unicode.html#toUpper>`_ for a version that works for any Unicode
  ## character.
  runnableExamples:
    doAssert toUpperAscii('a') == 'A'
    doAssert toUpperAscii('E') == 'E'
  if c in {'a'..'z'}:
    result = chr(ord(c) - (ord('a') - ord('A')))
  else:
    result = c

proc toUpperAscii*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuToUpperAsciiStr".} =
  ## Converts `s` into upper case.
  ##
  ## This works only for the letters ``A-Z``.  See `unicode.toUpper
  ## <unicode.html#toUpper>`_ for a version that works for any Unicode
  ## character.
  runnableExamples:
    doAssert toUpperAscii("FooBar!") == "FOOBAR!"
  toImpl toUpperAscii

proc capitalizeAscii*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuCapitalizeAscii".} =
  ## Converts the first character of `s` into upper case.
  ##
  ## This works only for the letters ``A-Z``.
  runnableExamples:
    doAssert capitalizeAscii("foo") == "Foo"
    doAssert capitalizeAscii("-bar") == "-bar"
  if s.len == 0: result = ""
  else: result = toUpperAscii(s[0]) & substr(s, 1)

proc normalize*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuNormalize".} =
  ## Normalizes the string `s`.
  ##
  ## That means to convert it to lower case and remove any '_'. This
  ## should NOT be used to normalize Nim identifier names.
  runnableExamples:
    doAssert normalize("Foo_bar") == "foobar"
    doAssert normalize("Foo Bar") == "foo bar"
  result = newString(s.len)
  var j = 0
  for i in 0..len(s) - 1:
    if s[i] in {'A'..'Z'}:
      result[j] = chr(ord(s[i]) + (ord('a') - ord('A')))
      inc j
    elif s[i] != '_':
      result[j] = s[i]
      inc j
  if j != s.len: setLen(result, j)

proc cmpIgnoreCase*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuCmpIgnoreCase", procvar.} =
  ## Compares two strings in a case insensitive manner. Returns:
  ##
  ## | 0 iff a == b
  ## | < 0 iff a < b
  ## | > 0 iff a > b
  runnableExamples:
    doAssert cmpIgnoreCase("FooBar", "foobar") == 0
    doAssert cmpIgnoreCase("bar", "Foo") < 0
    doAssert cmpIgnoreCase("Foo5", "foo4") > 0
  var i = 0
  var m = min(a.len, b.len)
  while i < m:
    result = ord(toLowerAscii(a[i])) - ord(toLowerAscii(b[i]))
    if result != 0: return
    inc(i)
  result = a.len - b.len

{.push checks: off, line_trace: off .} # this is a hot-spot in the compiler!
                                       # thus we compile without checks here

proc cmpIgnoreStyle*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuCmpIgnoreStyle", procvar.} =
  ## Semantically the same as ``cmp(normalize(a), normalize(b))``. It
  ## is just optimized to not allocate temporary strings. This should
  ## NOT be used to compare Nim identifier names. use `macros.eqIdent`
  ## for that. Returns:
  ##
  ## | 0 iff a == b
  ## | < 0 iff a < b
  ## | > 0 iff a > b
  runnableExamples:
    doAssert cmpIgnoreStyle("foo_bar", "FooBar") == 0
    doAssert cmpIgnoreStyle("foo_bar_5", "FooBar4") > 0
  var i = 0
  var j = 0
  while true:
    while i < a.len and a[i] == '_': inc i
    while j < b.len and b[j] == '_': inc j
    var aa = if i < a.len: toLowerAscii(a[i]) else: '\0'
    var bb = if j < b.len: toLowerAscii(b[j]) else: '\0'
    result = ord(aa) - ord(bb)
    if result != 0: return result
    # the characters are identical:
    if i >= a.len:
      # both cursors at the end:
      if j >= b.len: return 0
      # not yet at the end of 'b':
      return -1
    elif j >= b.len:
      return 1
    inc i
    inc j

proc strip*(s: string, leading = true, trailing = true,
            chars: set[char] = Whitespace): string
  {.noSideEffect, rtl, extern: "nsuStrip".} =
  ## Strips leading or trailing `chars` from `s` and returns
  ## the resulting string.
  ##
  ## If `leading` is true, leading `chars` are stripped.
  ## If `trailing` is true, trailing `chars` are stripped.
  ## If both are false, the string is returned unchanged.
  runnableExamples:
    doAssert " vhellov ".strip().strip(trailing = false, chars = {'v'}) == "hellov"
  var
    first = 0
    last = len(s)-1
  if leading:
    while first <= last and s[first] in chars: inc(first)
  if trailing:
    while last >= 0 and s[last] in chars: dec(last)
  result = substr(s, first, last)

proc toOctal*(c: char): string {.noSideEffect, rtl, extern: "nsuToOctal".} =
  ## Converts a character `c` to its octal representation.
  ##
  ## The resulting string may not have a leading zero. Its length is always
  ## exactly 3.
  runnableExamples:
    doAssert toOctal('!') == "041" 
  result = newString(3)
  var val = ord(c)
  for i in countdown(2, 0):
    result[i] = chr(val mod 8 + ord('0'))
    val = val div 8

proc isNilOrEmpty*(s: string): bool {.noSideEffect, procvar, rtl,
                                      extern: "nsuIsNilOrEmpty",
                                      deprecated: "use 'x.len == 0' instead".} =
  ## Checks if `s` is nil or empty.
  result = len(s) == 0

proc isNilOrWhitespace*(s: string): bool {.noSideEffect, procvar, rtl, extern: "nsuIsNilOrWhitespace".} =
  ## Checks if `s` is nil or consists entirely of whitespace characters.
  result = true
  for c in s:
    if not c.isSpaceAscii():
      return false

proc substrEq(s: string, pos: int, substr: string): bool =
  var i = 0
  var length = substr.len
  while i < length and s[pos+i] == substr[i]:
    inc i
  return i == length

# --------- Private templates for different split separators -----------

template stringHasSep(s: string, index: int, seps: set[char]): bool =
  s[index] in seps

template stringHasSep(s: string, index: int, sep: char): bool =
  s[index] == sep

template stringHasSep(s: string, index: int, sep: string): bool =
  s.substrEq(index, sep)

template splitCommon(s, sep, maxsplit, sepLen) =
  ## Common code for split procedures
  var last = 0
  var splits = maxsplit

  while last <= len(s):
    var first = last
    while last < len(s) and not stringHasSep(s, last, sep):
      inc(last)
    if splits == 0: last = len(s)
    yield substr(s, first, last-1)
    if splits == 0: break
    dec(splits)
    inc(last, sepLen)

template oldSplit(s, seps, maxsplit) =
  var last = 0
  var splits = maxsplit
  assert(not ('\0' in seps))
  while last < len(s):
    while last < len(s) and s[last] in seps: inc(last)
    var first = last
    while last < len(s) and s[last] notin seps: inc(last)
    if first <= last-1:
      if splits == 0: last = len(s)
      yield substr(s, first, last-1)
      if splits == 0: break
      dec(splits)

iterator split*(s: string, seps: set[char] = Whitespace,
                maxsplit: int = -1): string =
  ## Splits the string `s` into substrings using a group of separators.
  ##
  ## Substrings are separated by a substring containing only `seps`.
  ##
  ## .. code-block:: nim
  ##   for word in split("this\lis an\texample"):
  ##     writeLine(stdout, word)
  ##
  ## ...generates this output:
  ##
  ## .. code-block::
  ##   "this"
  ##   "is"
  ##   "an"
  ##   "example"
  ##
  ## And the following code:
  ##
  ## .. code-block:: nim
  ##   for word in split("this:is;an$example", {';', ':', '$'}):
  ##     writeLine(stdout, word)
  ##
  ## ...produces the same output as the first example. The code:
  ##
  ## .. code-block:: nim
  ##   let date = "2012-11-20T22:08:08.398990"
  ##   let separators = {' ', '-', ':', 'T'}
  ##   for number in split(date, separators):
  ##     writeLine(stdout, number)
  ##
  ## ...results in:
  ##
  ## .. code-block::
  ##   "2012"
  ##   "11"
  ##   "20"
  ##   "22"
  ##   "08"
  ##   "08.398990"
  ##
  splitCommon(s, seps, maxsplit, 1)

iterator splitWhitespace*(s: string, maxsplit: int = -1): string =
  ## Splits the string ``s`` at whitespace stripping leading and trailing
  ## whitespace if necessary. If ``maxsplit`` is specified and is positive,
  ## no more than ``maxsplit`` splits is made.
  ##
  ## The following code:
  ##
  ## .. code-block:: nim
  ##   let s = "  foo \t bar  baz  "
  ##   for ms in [-1, 1, 2, 3]:
  ##     echo "------ maxsplit = ", ms, ":"
  ##     for item in s.splitWhitespace(maxsplit=ms):
  ##       echo '"', item, '"'
  ##
  ## ...results in:
  ##
  ## .. code-block::
  ##   ------ maxsplit = -1:
  ##   "foo"
  ##   "bar"
  ##   "baz"
  ##   ------ maxsplit = 1:
  ##   "foo"
  ##   "bar  baz  "
  ##   ------ maxsplit = 2:
  ##   "foo"
  ##   "bar"
  ##   "baz  "
  ##   ------ maxsplit = 3:
  ##   "foo"
  ##   "bar"
  ##   "baz"
  ##
  oldSplit(s, Whitespace, maxsplit)

template accResult(iter: untyped) =
  result = @[]
  for x in iter: add(result, x)

proc splitWhitespace*(s: string, maxsplit: int = -1): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitWhitespace".} =
  ## The same as the `splitWhitespace <#splitWhitespace.i,string,int>`_
  ## iterator, but is a proc that returns a sequence of substrings.
  accResult(splitWhitespace(s, maxsplit))

iterator split*(s: string, sep: char, maxsplit: int = -1): string =
  ## Splits the string `s` into substrings using a single separator.
  ##
  ## Substrings are separated by the character `sep`.
  ## The code:
  ##
  ## .. code-block:: nim
  ##   for word in split(";;this;is;an;;example;;;", ';'):
  ##     writeLine(stdout, word)
  ##
  ## Results in:
  ##
  ## .. code-block::
  ##   ""
  ##   ""
  ##   "this"
  ##   "is"
  ##   "an"
  ##   ""
  ##   "example"
  ##   ""
  ##   ""
  ##   ""
  ##
  splitCommon(s, sep, maxsplit, 1)

iterator split*(s: string, sep: string, maxsplit: int = -1): string =
  ## Splits the string `s` into substrings using a string separator.
  ##
  ## Substrings are separated by the string `sep`.
  ## The code:
  ##
  ## .. code-block:: nim
  ##   for word in split("thisDATAisDATAcorrupted", "DATA"):
  ##     writeLine(stdout, word)
  ##
  ## Results in:
  ##
  ## .. code-block::
  ##   "this"
  ##   "is"
  ##   "corrupted"
  ##
  splitCommon(s, sep, maxsplit, sep.len)

template rsplitCommon(s, sep, maxsplit, sepLen) =
  ## Common code for rsplit functions
  var
    last = s.len - 1
    first = last
    splits = maxsplit
    startPos = 0
  # go to -1 in order to get separators at the beginning
  while first >= -1:
    while first >= 0 and not stringHasSep(s, first, sep):
      dec(first)
    if splits == 0:
      # No more splits means set first to the beginning
      first = -1
    if first == -1:
      startPos = 0
    else:
      startPos = first + sepLen
    yield substr(s, startPos, last)
    if splits == 0: break
    dec(splits)
    dec(first)
    last = first

iterator rsplit*(s: string, seps: set[char] = Whitespace,
                 maxsplit: int = -1): string =
  ## Splits the string `s` into substrings from the right using a
  ## string separator. Works exactly the same as `split iterator
  ## <#split.i,string,char,int>`_ except in reverse order.
  ##
  ## .. code-block:: nim
  ##   for piece in "foo bar".rsplit(WhiteSpace):
  ##     echo piece
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "bar"
  ##   "foo"
  ##
  ## Substrings are separated from the right by the set of chars `seps`
  rsplitCommon(s, seps, maxsplit, 1)

iterator rsplit*(s: string, sep: char,
                 maxsplit: int = -1): string =
  ## Splits the string `s` into substrings from the right using a
  ## string separator. Works exactly the same as `split iterator
  ## <#split.i,string,char,int>`_ except in reverse order.
  ##
  ## .. code-block:: nim
  ##   for piece in "foo:bar".rsplit(':'):
  ##     echo piece
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "bar"
  ##   "foo"
  ##
  ## Substrings are separated from the right by the char `sep`
  rsplitCommon(s, sep, maxsplit, 1)

iterator rsplit*(s: string, sep: string, maxsplit: int = -1,
                 keepSeparators: bool = false): string =
  ## Splits the string `s` into substrings from the right using a
  ## string separator. Works exactly the same as `split iterator
  ## <#split.i,string,string,int>`_ except in reverse order.
  ##
  ## .. code-block:: nim
  ##   for piece in "foothebar".rsplit("the"):
  ##     echo piece
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "bar"
  ##   "foo"
  ##
  ## Substrings are separated from the right by the string `sep`
  rsplitCommon(s, sep, maxsplit, sep.len)

iterator splitLines*(s: string, keepEol = false): string =
  ## Splits the string `s` into its containing lines.
  ##
  ## Every `character literal <manual.html#character-literals>`_ newline
  ## combination (CR, LF, CR-LF) is supported. The result strings contain no
  ## trailing end of line characters unless parameter ``keepEol`` is set to
  ## ``true``.
  ##
  ## Example:
  ##
  ## .. code-block:: nim
  ##   for line in splitLines("\nthis\nis\nan\n\nexample\n"):
  ##     writeLine(stdout, line)
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   ""
  ##   "this"
  ##   "is"
  ##   "an"
  ##   ""
  ##   "example"
  ##   ""
  var first = 0
  var last = 0
  var eolpos = 0
  while true:
    while last < s.len and s[last] notin {'\c', '\l'}: inc(last)

    eolpos = last
    if last < s.len:
      if s[last] == '\l': inc(last)
      elif s[last] == '\c':
        inc(last)
        if last < s.len and s[last] == '\l': inc(last)

    yield substr(s, first, if keepEol: last-1 else: eolpos-1)

    # no eol characters consumed means that the string is over
    if eolpos == last:
      break

    first = last

proc splitLines*(s: string, keepEol = false): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitLines".} =
  ## The same as the `splitLines <#splitLines.i,string>`_ iterator, but is a
  ## proc that returns a sequence of substrings.
  accResult(splitLines(s, keepEol=keepEol))

proc countLines*(s: string): int {.noSideEffect,
  rtl, extern: "nsuCountLines".} =
  ## Returns the number of lines in the string `s`.
  ##
  ## This is the same as ``len(splitLines(s))``, but much more efficient
  ## because it doesn't modify the string creating temporal objects. Every
  ## `character literal <manual.html#character-literals>`_ newline combination
  ## (CR, LF, CR-LF) is supported.
  ##
  ## In this context, a line is any string seperated by a newline combination.
  ## A line can be an empty string.
  runnableExamples:
    doAssert countLines("First line\l and second line.") == 2
  result = 1
  var i = 0
  while i < s.len:
    case s[i]
    of '\c':
      if i+1 < s.len and s[i+1] == '\l': inc i
      inc result
    of '\l': inc result
    else: discard
    inc i

proc split*(s: string, seps: set[char] = Whitespace, maxsplit: int = -1): seq[string] {.
  noSideEffect, rtl, extern: "nsuSplitCharSet".} =
  ## The same as the `split iterator <#split.i,string,set[char],int>`_, but is a
  ## proc that returns a sequence of substrings.
  runnableExamples:
    doAssert "a,b;c".split({',', ';'}) == @["a", "b", "c"]
    doAssert "".split({' '}) == @[""]
  accResult(split(s, seps, maxsplit))

proc split*(s: string, sep: char, maxsplit: int = -1): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitChar".} =
  ## The same as the `split iterator <#split.i,string,char,int>`_, but is a proc
  ## that returns a sequence of substrings.
  runnableExamples:
    doAssert "a,b,c".split(',') == @["a", "b", "c"]
    doAssert "".split(' ') == @[""]
  accResult(split(s, sep, maxsplit))

proc split*(s: string, sep: string, maxsplit: int = -1): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitString".} =
  ## Splits the string `s` into substrings using a string separator.
  ##
  ## Substrings are separated by the string `sep`. This is a wrapper around the
  ## `split iterator <#split.i,string,string,int>`_.
  runnableExamples:
    doAssert "a,b,c".split(",") == @["a", "b", "c"]
    doAssert "a man a plan a canal panama".split("a ") == @["", "man ", "plan ", "canal panama"]
    doAssert "".split("Elon Musk") == @[""]
    doAssert "a  largely    spaced sentence".split(" ") == @["a", "", "largely", "", "", "", "spaced", "sentence"]

    doAssert "a  largely    spaced sentence".split(" ", maxsplit=1) == @["a", " largely    spaced sentence"]
  doAssert(sep.len > 0)

  accResult(split(s, sep, maxsplit))

proc rsplit*(s: string, seps: set[char] = Whitespace,
             maxsplit: int = -1): seq[string]
             {.noSideEffect, rtl, extern: "nsuRSplitCharSet".} =
  ## The same as the `rsplit iterator <#rsplit.i,string,set[char],int>`_, but is a
  ## proc that returns a sequence of substrings.
  ##
  ## A possible common use case for `rsplit` is path manipulation,
  ## particularly on systems that don't use a common delimiter.
  ##
  ## For example, if a system had `#` as a delimiter, you could
  ## do the following to get the tail of the path:
  ##
  ## .. code-block:: nim
  ##   var tailSplit = rsplit("Root#Object#Method#Index", {'#'}, maxsplit=1)
  ##
  ## Results in `tailSplit` containing:
  ##
  ## .. code-block:: nim
  ##   @["Root#Object#Method", "Index"]
  ##
  accResult(rsplit(s, seps, maxsplit))
  result.reverse()

proc rsplit*(s: string, sep: char, maxsplit: int = -1): seq[string]
             {.noSideEffect, rtl, extern: "nsuRSplitChar".} =
  ## The same as the `rsplit iterator <#rsplit.i,string,char,int>`_, but is a proc
  ## that returns a sequence of substrings.
  ##
  ## A possible common use case for `rsplit` is path manipulation,
  ## particularly on systems that don't use a common delimiter.
  ##
  ## For example, if a system had `#` as a delimiter, you could
  ## do the following to get the tail of the path:
  ##
  ## .. code-block:: nim
  ##   var tailSplit = rsplit("Root#Object#Method#Index", '#', maxsplit=1)
  ##
  ## Results in `tailSplit` containing:
  ##
  ## .. code-block:: nim
  ##   @["Root#Object#Method", "Index"]
  ##
  accResult(rsplit(s, sep, maxsplit))
  result.reverse()

proc rsplit*(s: string, sep: string, maxsplit: int = -1): seq[string]
             {.noSideEffect, rtl, extern: "nsuRSplitString".} =
  ## The same as the `rsplit iterator <#rsplit.i,string,string,int>`_, but is a proc
  ## that returns a sequence of substrings.
  ##
  ## A possible common use case for `rsplit` is path manipulation,
  ## particularly on systems that don't use a common delimiter.
  ##
  ## For example, if a system had `#` as a delimiter, you could
  ## do the following to get the tail of the path:
  ##
  ## .. code-block:: nim
  ##   var tailSplit = rsplit("Root#Object#Method#Index", "#", maxsplit=1)
  ##
  ## Results in `tailSplit` containing:
  ##
  ## .. code-block:: nim
  ##   @["Root#Object#Method", "Index"]
  ##
  runnableExamples:
    doAssert "a  largely    spaced sentence".rsplit(" ", maxsplit=1) == @["a  largely    spaced", "sentence"]

    doAssert "a,b,c".rsplit(",") == @["a", "b", "c"]
    doAssert "a man a plan a canal panama".rsplit("a ") == @["", "man ", "plan ", "canal panama"]
    doAssert "".rsplit("Elon Musk") == @[""]
    doAssert "a  largely    spaced sentence".rsplit(" ") == @["a", "", "largely", "", "", "", "spaced", "sentence"]
  accResult(rsplit(s, sep, maxsplit))
  result.reverse()

proc toHex*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToHex".} =
  ## Converts `x` to its hexadecimal representation.
  ##
  ## The resulting string will be exactly `len` characters long. No prefix like
  ## ``0x`` is generated. `x` is treated as an unsigned value.
  runnableExamples:
    doAssert toHex(1984, 6) == "0007C0"
    doAssert toHex(1984, 2) == "C0"
  const
    HexChars = "0123456789ABCDEF"
  var
    n = x
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = HexChars[int(n and 0xF)]
    n = n shr 4
    # handle negative overflow
    if n == 0 and x < 0: n = -1

proc toHex*[T: SomeInteger](x: T): string =
  ## Shortcut for ``toHex(x, T.sizeOf * 2)``
  runnableExamples:
    doAssert toHex(1984'i64) == "00000000000007C0"
  toHex(BiggestInt(x), T.sizeOf * 2)

proc toHex*(s: string): string {.noSideEffect, rtl.} =
  ## Converts a bytes string to its hexadecimal representation.
  ##
  ## The output is twice the input long. No prefix like
  ## ``0x`` is generated.
  const HexChars = "0123456789ABCDEF"
  result = newString(s.len * 2)
  for pos, c in s:
    var n = ord(c)
    result[pos * 2 + 1] = HexChars[n and 0xF]
    n = n shr 4
    result[pos * 2] = HexChars[n]

proc intToStr*(x: int, minchars: Positive = 1): string {.noSideEffect,
  rtl, extern: "nsuIntToStr".} =
  ## Converts `x` to its decimal representation.
  ##
  ## The resulting string will be minimally `minchars` characters long. This is
  ## achieved by adding leading zeros.
  runnableExamples:
    doAssert intToStr(1984) == "1984"
    doAssert intToStr(1984, 6) == "001984" 
  result = $abs(x)
  for i in 1 .. minchars - len(result):
    result = '0' & result
  if x < 0:
    result = '-' & result

proc parseInt*(s: string): int {.noSideEffect, procvar,
  rtl, extern: "nsuParseInt".} =
  ## Parses a decimal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  runnableExamples:
    doAssert parseInt("-0042") == -42
  let L = parseutils.parseInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid integer: " & s)

proc parseBiggestInt*(s: string): BiggestInt {.noSideEffect, procvar,
  rtl, extern: "nsuParseBiggestInt".} =
  ## Parses a decimal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  let L = parseutils.parseBiggestInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid integer: " & s)

proc parseUInt*(s: string): uint {.noSideEffect, procvar,
  rtl, extern: "nsuParseUInt".} =
  ## Parses a decimal unsigned integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  let L = parseutils.parseUInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid unsigned integer: " & s)

proc parseBiggestUInt*(s: string): BiggestUInt {.noSideEffect, procvar,
  rtl, extern: "nsuParseBiggestUInt".} =
  ## Parses a decimal unsigned integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  let L = parseutils.parseBiggestUInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid unsigned integer: " & s)

proc parseFloat*(s: string): float {.noSideEffect, procvar,
  rtl, extern: "nsuParseFloat".} =
  ## Parses a decimal floating point value contained in `s`. If `s` is not
  ## a valid floating point number, `ValueError` is raised. ``NAN``,
  ## ``INF``, ``-INF`` are also supported (case insensitive comparison).
  runnableExamples:
    doAssert parseFloat("3.14") == 3.14
    doAssert parseFloat("inf") == 1.0/0
  let L = parseutils.parseFloat(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid float: " & s)

proc parseBinInt*(s: string): int {.noSideEffect, procvar,
  rtl, extern: "nsuParseBinInt".} =
  ## Parses a binary integer value contained in `s`.
  ##
  ## If `s` is not a valid binary integer, `ValueError` is raised. `s` can have
  ## one of the following optional prefixes: ``0b``, ``0B``. Underscores within
  ## `s` are ignored.
  let L = parseutils.parseBin(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid binary integer: " & s)

proc parseOctInt*(s: string): int {.noSideEffect,
  rtl, extern: "nsuParseOctInt".} =
  ## Parses an octal integer value contained in `s`.
  ##
  ## If `s` is not a valid oct integer, `ValueError` is raised. `s` can have one
  ## of the following optional prefixes: ``0o``, ``0O``.  Underscores within
  ## `s` are ignored.
  let L = parseutils.parseOct(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid oct integer: " & s)

proc parseHexInt*(s: string): int {.noSideEffect, procvar,
  rtl, extern: "nsuParseHexInt".} =
  ## Parses a hexadecimal integer value contained in `s`.
  ##
  ## If `s` is not a valid hex integer, `ValueError` is raised. `s` can have one
  ## of the following optional prefixes: ``0x``, ``0X``, ``#``.  Underscores
  ## within `s` are ignored.
  let L = parseutils.parseHex(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid hex integer: " & s)

proc generateHexCharToValueMap(): string =
  ## Generate a string to map a hex digit to uint value
  result = ""
  for inp in 0..255:
    let ch = chr(inp)
    let o =
      case ch:
        of '0'..'9': inp - ord('0')
        of 'a'..'f': inp - ord('a') + 10
        of 'A'..'F': inp - ord('A') + 10
        else: 17  # indicates an invalid hex char
    result.add chr(o)

const hexCharToValueMap = generateHexCharToValueMap()

proc parseHexStr*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuParseHexStr".} =
  ## Convert hex-encoded string to byte string, e.g.:
  ##
  ## .. code-block:: nim
  ##    hexToStr("00ff") == "\0\255"
  ##
  ## Raises ``ValueError`` for an invalid hex values. The comparison is
  ## case-insensitive.
  if s.len mod 2 != 0:
    raise newException(ValueError, "Incorrect hex string len")
  result = newString(s.len div 2)
  var buf = 0
  for pos, c in s:
    let val = hexCharToValueMap[ord(c)].ord
    if val == 17:
      raise newException(ValueError, "Invalid hex char " & repr(c))
    if pos mod 2 == 0:
      buf = val
    else:
      result[pos div 2] = chr(val + buf shl 4)

proc parseBool*(s: string): bool =
  ## Parses a value into a `bool`.
  ##
  ## If ``s`` is one of the following values: ``y, yes, true, 1, on``, then
  ## returns `true`. If ``s`` is one of the following values: ``n, no, false,
  ## 0, off``, then returns `false`.  If ``s`` is something else a
  ## ``ValueError`` exception is raised.
  case normalize(s)
  of "y", "yes", "true", "1", "on": result = true
  of "n", "no", "false", "0", "off": result = false
  else: raise newException(ValueError, "cannot interpret as a bool: " & s)

proc parseEnum*[T: enum](s: string): T =
  ## Parses an enum ``T``.
  ##
  ## Raises ``ValueError`` for an invalid value in `s`. The comparison is
  ## done in a style insensitive way.
  for e in low(T)..high(T):
    if cmpIgnoreStyle(s, $e) == 0:
      return e
  raise newException(ValueError, "invalid enum value: " & s)

proc parseEnum*[T: enum](s: string, default: T): T =
  ## Parses an enum ``T``.
  ##
  ## Uses `default` for an invalid value in `s`. The comparison is done in a
  ## style insensitive way.
  for e in low(T)..high(T):
    if cmpIgnoreStyle(s, $e) == 0:
      return e
  result = default

proc repeat*(c: char, count: Natural): string {.noSideEffect,
  rtl, extern: "nsuRepeatChar".} =
  ## Returns a string of length `count` consisting only of
  ## the character `c`. You can use this proc to left align strings. Example:
  ##
  ## .. code-block:: nim
  ##   proc tabexpand(indent: int, text: string, tabsize: int = 4) =
  ##     echo '\t'.repeat(indent div tabsize), ' '.repeat(indent mod tabsize),
  ##         text
  ##
  ##   tabexpand(4, "At four")
  ##   tabexpand(5, "At five")
  ##   tabexpand(6, "At six")
  result = newString(count)
  for i in 0..count-1: result[i] = c

proc repeat*(s: string, n: Natural): string {.noSideEffect,
  rtl, extern: "nsuRepeatStr".} =
  ## Returns String `s` concatenated `n` times.  Example:
  ##
  ## .. code-block:: nim
  ##   echo "+++ STOP ".repeat(4), "+++"
  result = newStringOfCap(n * s.len)
  for i in 1..n: result.add(s)

template spaces*(n: Natural): string = repeat(' ', n)
  ## Returns a String with `n` space characters. You can use this proc
  ## to left align strings. Example:
  ##
  ## .. code-block:: nim
  ##   let
  ##     width = 15
  ##     text1 = "Hello user!"
  ##     text2 = "This is a very long string"
  ##   echo text1 & spaces(max(0, width - text1.len)) & "|"
  ##   echo text2 & spaces(max(0, width - text2.len)) & "|"

proc align*(s: string, count: Natural, padding = ' '): string {.
  noSideEffect, rtl, extern: "nsuAlignString".} =
  ## Aligns a string `s` with `padding`, so that it is of length `count`.
  ##
  ## `padding` characters (by default spaces) are added before `s` resulting in
  ## right alignment. If ``s.len >= count``, no spaces are added and `s` is
  ## returned unchanged. If you need to left align a string use the `alignLeft
  ## proc <#alignLeft>`_. Example:
  ##
  ## .. code-block:: nim
  ##   assert align("abc", 4) == " abc"
  ##   assert align("a", 0) == "a"
  ##   assert align("1232", 6) == "  1232"
  ##   assert align("1232", 6, '#') == "##1232"
  if s.len < count:
    result = newString(count)
    let spaces = count - s.len
    for i in 0..spaces-1: result[i] = padding
    for i in spaces..count-1: result[i] = s[i-spaces]
  else:
    result = s

proc alignLeft*(s: string, count: Natural, padding = ' '): string {.noSideEffect.} =
  ## Left-Aligns a string `s` with `padding`, so that it is of length `count`.
  ##
  ## `padding` characters (by default spaces) are added after `s` resulting in
  ## left alignment. If ``s.len >= count``, no spaces are added and `s` is
  ## returned unchanged. If you need to right align a string use the `align
  ## proc <#align>`_. Example:
  ##
  ## .. code-block:: nim
  ##   assert alignLeft("abc", 4) == "abc "
  ##   assert alignLeft("a", 0) == "a"
  ##   assert alignLeft("1232", 6) == "1232  "
  ##   assert alignLeft("1232", 6, '#') == "1232##"
  if s.len < count:
    result = newString(count)
    if s.len > 0:
      result[0 .. (s.len - 1)] = s
    for i in s.len ..< count:
      result[i] = padding
  else:
    result = s

iterator tokenize*(s: string, seps: set[char] = Whitespace): tuple[
  token: string, isSep: bool] =
  ## Tokenizes the string `s` into substrings.
  ##
  ## Substrings are separated by a substring containing only `seps`.
  ## Examples:
  ##
  ## .. code-block:: nim
  ##   for word in tokenize("  this is an  example  "):
  ##     writeLine(stdout, word)
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   ("  ", true)
  ##   ("this", false)
  ##   (" ", true)
  ##   ("is", false)
  ##   (" ", true)
  ##   ("an", false)
  ##   ("  ", true)
  ##   ("example", false)
  ##   ("  ", true)
  var i = 0
  while true:
    var j = i
    var isSep = j < s.len and s[j] in seps
    while j < s.len and (s[j] in seps) == isSep: inc(j)
    if j > i:
      yield (substr(s, i, j-1), isSep)
    else:
      break
    i = j

proc wordWrap*(s: string, maxLineWidth = 80,
               splitLongWords = true,
               seps: set[char] = Whitespace,
               newLine = "\n"): string {.
               noSideEffect, rtl, extern: "nsuWordWrap".} =
  ## Word wraps `s`.
  result = newStringOfCap(s.len + s.len shr 6)
  var spaceLeft = maxLineWidth
  var lastSep = ""
  for word, isSep in tokenize(s, seps):
    if isSep:
      lastSep = word
      spaceLeft = spaceLeft - len(word)
      continue
    if len(word) > spaceLeft:
      if splitLongWords and len(word) > maxLineWidth:
        result.add(substr(word, 0, spaceLeft-1))
        var w = spaceLeft
        var wordLeft = len(word) - spaceLeft
        while wordLeft > 0:
          result.add(newLine)
          var L = min(maxLineWidth, wordLeft)
          spaceLeft = maxLineWidth - L
          result.add(substr(word, w, w+L-1))
          inc(w, L)
          dec(wordLeft, L)
      else:
        spaceLeft = maxLineWidth - len(word)
        result.add(newLine)
        result.add(word)
    else:
      spaceLeft = spaceLeft - len(word)
      result.add(lastSep & word)
      lastSep.setLen(0)

proc indent*(s: string, count: Natural, padding: string = " "): string
    {.noSideEffect, rtl, extern: "nsuIndent".} =
  ## Indents each line in ``s`` by ``count`` amount of ``padding``.
  ##
  ## **Note:** This does not preserve the new line characters used in ``s``.
  runnableExamples:
    doAssert indent("First line\c\l and second line.", 2) == "  First line\l   and second line."
  result = ""
  var i = 0
  for line in s.splitLines():
    if i != 0:
      result.add("\n")
    for j in 1..count:
      result.add(padding)
    result.add(line)
    i.inc

proc unindent*(s: string, count: Natural, padding: string = " "): string
    {.noSideEffect, rtl, extern: "nsuUnindent".} =
  ## Unindents each line in ``s`` by ``count`` amount of ``padding``.
  ##
  ## **Note:** This does not preserve the new line characters used in ``s``.
  runnableExamples:
    doAssert unindent("  First line\l   and second line", 3) == "First line\land second line"
  result = ""
  var i = 0
  for line in s.splitLines():
    if i != 0:
      result.add("\n")
    var indentCount = 0
    for j in 0..<count.int:
      indentCount.inc
      if j + padding.len-1 >= line.len or line[j .. j + padding.len-1] != padding:
        indentCount = j
        break
    result.add(line[indentCount*padding.len .. ^1])
    i.inc

proc unindent*(s: string): string
    {.noSideEffect, rtl, extern: "nsuUnindentAll".} =
  ## Removes all indentation composed of whitespace from each line in ``s``.
  ##
  ## For example:
  ##
  ## .. code-block:: nim
  ##   const x = """
  ##     Hello
  ##     There
  ##   """.unindent()
  ##
  ##   doAssert x == "Hello\nThere\n"
  unindent(s, 1000) # TODO: Passing a 1000 is a bit hackish.

proc startsWith*(s, prefix: string): bool {.noSideEffect,
  rtl, extern: "nsuStartsWith".} =
  ## Returns true iff ``s`` starts with ``prefix``.
  ##
  ## If ``prefix == ""`` true is returned.
  var i = 0
  while true:
    if i >= prefix.len: return true
    if i >= s.len or s[i] != prefix[i]: return false
    inc(i)

proc startsWith*(s: string, prefix: char): bool {.noSideEffect, inline.} =
  ## Returns true iff ``s`` starts with ``prefix``.
  result = s.len > 0 and s[0] == prefix

proc endsWith*(s, suffix: string): bool {.noSideEffect,
  rtl, extern: "nsuEndsWith".} =
  ## Returns true iff ``s`` ends with ``suffix``.
  ##
  ## If ``suffix == ""`` true is returned.
  var i = 0
  var j = len(s) - len(suffix)
  while i+j <% s.len:
    if s[i+j] != suffix[i]: return false
    inc(i)
  if i >= suffix.len: return true

proc endsWith*(s: string, suffix: char): bool {.noSideEffect, inline.} =
  ## Returns true iff ``s`` ends with ``suffix``.
  result = s.len > 0 and s[s.high] == suffix

proc continuesWith*(s, substr: string, start: Natural): bool {.noSideEffect,
  rtl, extern: "nsuContinuesWith".} =
  ## Returns true iff ``s`` continues with ``substr`` at position ``start``.
  ##
  ## If ``substr == ""`` true is returned.
  var i = 0
  while true:
    if i >= substr.len: return true
    if i+start >= s.len or s[i+start] != substr[i]: return false
    inc(i)

proc addSep*(dest: var string, sep = ", ", startLen: Natural = 0)
  {.noSideEffect, inline.} =
  ## Adds a separator to `dest` only if its length is bigger than `startLen`.
  ##
  ## A shorthand for:
  ##
  ## .. code-block:: nim
  ##   if dest.len > startLen: add(dest, sep)
  ##
  ## This is often useful for generating some code where the items need to
  ## be *separated* by `sep`. `sep` is only added if `dest` is longer than
  ## `startLen`. The following example creates a string describing
  ## an array of integers.
  runnableExamples:
     var arr = "["
     for x in items([2, 3, 5, 7, 11]):
       addSep(arr, startLen=len("["))
       add(arr, $x)
     add(arr, "]")
  if dest.len > startLen: add(dest, sep)

proc allCharsInSet*(s: string, theSet: set[char]): bool =
  ## Returns true iff each character of `s` is in the set `theSet`.
  runnableExamples:
    doAssert allCharsInSet("aeea", {'a', 'e'}) == true
    doAssert allCharsInSet("", {'a', 'e'}) == true
  for c in items(s):
    if c notin theSet: return false
  return true

proc abbrev*(s: string, possibilities: openArray[string]): int =
  ## Returns the index of the first item in ``possibilities`` which starts with ``s``, if not ambiguous.
  ##
  ## Returns -1 if no item has been found and -2 if multiple items match.
  runnableExamples:
    doAssert abbrev("fac", ["college", "faculty", "industry"]) == 1
    doAssert abbrev("foo", ["college", "faculty", "industry"]) == -1 # Not found
    doAssert abbrev("fac", ["college", "faculty", "faculties"]) == -2 # Ambiguous
    doAssert abbrev("college", ["college", "colleges", "industry"]) == 0
  result = -1 # none found
  for i in 0..possibilities.len-1:
    if possibilities[i].startsWith(s):
      if possibilities[i] == s:
        # special case: exact match shouldn't be ambiguous
        return i
      if result >= 0: return -2 # ambiguous
      result = i

# ---------------------------------------------------------------------------

proc join*(a: openArray[string], sep: string = ""): string {.
  noSideEffect, rtl, extern: "nsuJoinSep".} =
  ## Concatenates all strings in `a` separating them with `sep`.
  runnableExamples:
    doAssert join(["A", "B", "Conclusion"], " -> ") == "A -> B -> Conclusion"
  if len(a) > 0:
    var L = sep.len * (a.len-1)
    for i in 0..high(a): inc(L, a[i].len)
    result = newStringOfCap(L)
    add(result, a[0])
    for i in 1..high(a):
      add(result, sep)
      add(result, a[i])
  else:
    result = ""

proc join*[T: not string](a: openArray[T], sep: string = ""): string {.
  noSideEffect, rtl.} =
  ## Converts all elements in `a` to strings using `$` and concatenates them
  ## with `sep`.
  runnableExamples:
    doAssert join([1, 2, 3], " -> ") == "1 -> 2 -> 3"
  result = ""
  for i, x in a:
    if i > 0:
      add(result, sep)
    add(result, $x)

type
  SkipTable* = array[char, int]

proc initSkipTable*(a: var SkipTable, sub: string)
  {.noSideEffect, rtl, extern: "nsuInitSkipTable".} =
  ## Preprocess table `a` for `sub`.
  let m = len(sub)
  var i = 0
  while i <= 0xff-7:
    a[chr(i + 0)] = m
    a[chr(i + 1)] = m
    a[chr(i + 2)] = m
    a[chr(i + 3)] = m
    a[chr(i + 4)] = m
    a[chr(i + 5)] = m
    a[chr(i + 6)] = m
    a[chr(i + 7)] = m
    i += 8

  for i in 0 ..< m - 1:
    a[sub[i]] = m - 1 - i

proc find*(a: SkipTable, s, sub: string, start: Natural = 0, last = 0): int
  {.noSideEffect, rtl, extern: "nsuFindStrA".} =
  ## Searches for `sub` in `s` inside range `start`..`last` using preprocessed table `a`.
  ## If `last` is unspecified, it defaults to `s.high`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.

  let
    last = if last==0: s.high else: last
    sLen = last - start + 1
    subLast = sub.len - 1

  if subLast == -1:
    # this was an empty needle string,
    # we count this as match in the first possible position:
    return start

  # This is an implementation of the Boyer-Moore Horspool algorithms
  # https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore%E2%80%93Horspool_algorithm
  var skip = start

  while last - skip >= subLast:
    var i = subLast
    while s[skip + i] == sub[i]:
      if i == 0:
        return skip
      dec i
    inc skip, a[s[skip + subLast]]

  return -1

when not (defined(js) or defined(nimdoc) or defined(nimscript)):
  proc c_memchr(cstr: pointer, c: char, n: csize): pointer {.
                importc: "memchr", header: "<string.h>" .}
  const hasCStringBuiltin = true
else:
  const hasCStringBuiltin = false

proc find*(s: string, sub: char, start: Natural = 0, last = 0): int {.noSideEffect,
  rtl, extern: "nsuFindChar".} =
  ## Searches for `sub` in `s` inside range `start`..`last`.
  ## If `last` is unspecified, it defaults to `s.high`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let last = if last==0: s.high else: last
  when nimvm:
    for i in int(start)..last:
      if sub == s[i]: return i
  else:
    when hasCStringBuiltin:
      let L = last-start+1
      if L > 0:
        let found = c_memchr(s[start].unsafeAddr, sub, L)
        if not found.isNil:
          return cast[ByteAddress](found) -% cast[ByteAddress](s.cstring)
    else:
      for i in int(start)..last:
        if sub == s[i]: return i
  return -1

proc find*(s, sub: string, start: Natural = 0, last = 0): int {.noSideEffect,
  rtl, extern: "nsuFindStr".} =
  ## Searches for `sub` in `s` inside range `start`..`last`.
  ## If `last` is unspecified, it defaults to `s.high`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  if sub.len > s.len: return -1
  if sub.len == 1: return find(s, sub[0], start, last)
  var a {.noinit.}: SkipTable
  initSkipTable(a, sub)
  result = find(a, s, sub, start, last)

proc find*(s: string, chars: set[char], start: Natural = 0, last = 0): int {.noSideEffect,
  rtl, extern: "nsuFindCharSet".} =
  ## Searches for `chars` in `s` inside range `start`..`last`.
  ## If `last` is unspecified, it defaults to `s.high`.
  ##
  ## If `s` contains none of the characters in `chars`, -1 is returned.
  let last = if last==0: s.high else: last
  for i in int(start)..last:
    if s[i] in chars: return i
  return -1

proc rfind*(s, sub: string, start: int = -1): int {.noSideEffect.} =
  ## Searches for `sub` in `s` in reverse, starting at `start` and going
  ## backwards to 0.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let realStart = if start == -1: s.len else: start
  for i in countdown(realStart-sub.len, 0):
    for j in 0..sub.len-1:
      result = i
      if sub[j] != s[i+j]:
        result = -1
        break
    if result != -1: return
  return -1

proc rfind*(s: string, sub: char, start: int = -1): int {.noSideEffect,
  rtl.} =
  ## Searches for `sub` in `s` in reverse starting at position `start`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let realStart = if start == -1: s.len-1 else: start
  for i in countdown(realStart, 0):
    if sub == s[i]: return i
  return -1

proc rfind*(s: string, chars: set[char], start: int = -1): int {.noSideEffect.} =
  ## Searches for `chars` in `s` in reverse starting at position `start`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let realStart = if start == -1: s.len-1 else: start
  for i in countdown(realStart, 0):
    if s[i] in chars: return i
  return -1

proc center*(s: string, width: int, fillChar: char = ' '): string {.
  noSideEffect, rtl, extern: "nsuCenterString".} =
  ## Return the contents of `s` centered in a string `width` long using
  ## `fillChar` as padding.
  ##
  ## The original string is returned if `width` is less than or equal
  ## to `s.len`.
  if width <= s.len: return s
  result = newString(width)
  # Left padding will be one fillChar
  # smaller if there are an odd number
  # of characters
  let
    charsLeft = (width - s.len)
    leftPadding = charsLeft div 2
  for i in 0 ..< width:
    if i >= leftPadding and i < leftPadding + s.len:
      # we are where the string should be located
      result[i] = s[i-leftPadding]
    else:
      # we are either before or after where
      # the string s should go
      result[i] = fillChar

proc count*(s: string, sub: string, overlapping: bool = false): int {.
  noSideEffect, rtl, extern: "nsuCountString".} =
  ## Count the occurrences of a substring `sub` in the string `s`.
  ## Overlapping occurrences of `sub` only count when `overlapping`
  ## is set to true.
  doAssert sub.len > 0
  var i = 0
  while true:
    i = s.find(sub, i)
    if i < 0: break
    if overlapping: inc i
    else: i += sub.len
    inc result

proc count*(s: string, sub: char): int {.noSideEffect,
  rtl, extern: "nsuCountChar".} =
  ## Count the occurrences of the character `sub` in the string `s`.
  for c in s:
    if c == sub: inc result

proc count*(s: string, subs: set[char]): int {.noSideEffect,
  rtl, extern: "nsuCountCharSet".} =
  ## Count the occurrences of the group of character `subs` in the string `s`.
  doAssert card(subs) > 0
  for c in s:
    if c in subs: inc result

proc quoteIfContainsWhite*(s: string): string {.deprecated.} =
  ## Returns ``'"' & s & '"'`` if `s` contains a space and does not
  ## start with a quote, else returns `s`.
  ##
  ## **DEPRECATED** as it was confused for shell quoting function.  For this
  ## application use `osproc.quoteShell <osproc.html#quoteShell>`_.
  if find(s, {' ', '\t'}) >= 0 and s[0] != '"': result = '"' & s & '"'
  else: result = s

proc contains*(s: string, c: char): bool {.noSideEffect.} =
  ## Same as ``find(s, c) >= 0``.
  return find(s, c) >= 0

proc contains*(s, sub: string): bool {.noSideEffect.} =
  ## Same as ``find(s, sub) >= 0``.
  return find(s, sub) >= 0

proc contains*(s: string, chars: set[char]): bool {.noSideEffect.} =
  ## Same as ``find(s, chars) >= 0``.
  return find(s, chars) >= 0

proc replace*(s, sub: string, by = ""): string {.noSideEffect,
  rtl, extern: "nsuReplaceStr".} =
  ## Replaces `sub` in `s` by the string `by`.
  result = ""
  let subLen = sub.len
  if subLen == 0:
    for c in s:
      add result, by
      add result, c
    add result, by
    return
  elif subLen == 1:
    # when the pattern is a single char, we use a faster
    # char-based search that doesn't need a skip table:
    let c = sub[0]
    let last = s.high
    var i = 0
    while true:
      let j = find(s, c, i, last)
      if j < 0: break
      add result, substr(s, i, j - 1)
      add result, by
      i = j + subLen
    # copy the rest:
    add result, substr(s, i)
  else:
    var a {.noinit.}: SkipTable
    initSkipTable(a, sub)
    let last = s.high
    var i = 0
    while true:
      let j = find(a, s, sub, i, last)
      if j < 0: break
      add result, substr(s, i, j - 1)
      add result, by
      i = j + subLen
    # copy the rest:
    add result, substr(s, i)

proc replace*(s: string, sub, by: char): string {.noSideEffect,
  rtl, extern: "nsuReplaceChar".} =
  ## Replaces `sub` in `s` by the character `by`.
  ##
  ## Optimized version of `replace <#replace,string,string>`_ for characters.
  result = newString(s.len)
  var i = 0
  while i < s.len:
    if s[i] == sub: result[i] = by
    else: result[i] = s[i]
    inc(i)

proc replaceWord*(s, sub: string, by = ""): string {.noSideEffect,
  rtl, extern: "nsuReplaceWord".} =
  ## Replaces `sub` in `s` by the string `by`.
  ##
  ## Each occurrence of `sub` has to be surrounded by word boundaries
  ## (comparable to ``\\w`` in regular expressions), otherwise it is not
  ## replaced.
  if sub.len == 0: return s
  const wordChars = {'a'..'z', 'A'..'Z', '0'..'9', '_', '\128'..'\255'}
  var a {.noinit.}: SkipTable
  result = ""
  initSkipTable(a, sub)
  var i = 0
  let last = s.high
  let sublen = max(sub.len, 1)
  while true:
    var j = find(a, s, sub, i, last)
    if j < 0: break
    # word boundary?
    if (j == 0 or s[j-1] notin wordChars) and
        (j+sub.len >= s.len or s[j+sub.len] notin wordChars):
      add result, substr(s, i, j - 1)
      add result, by
      i = j + sublen
    else:
      add result, substr(s, i, j)
      i = j + 1
  # copy the rest:
  add result, substr(s, i)

proc multiReplace*(s: string, replacements: varargs[(string, string)]): string {.noSideEffect.} =
  ## Same as replace, but specialized for doing multiple replacements in a single
  ## pass through the input string.
  ##
  ## multiReplace performs all replacements in a single pass, this means it can be used
  ## to swap the occurences of "a" and "b", for instance.
  ##
  ## If the resulting string is not longer than the original input string, only a single
  ## memory allocation is required.
  ##
  ## The order of the replacements does matter. Earlier replacements are preferred over later
  ## replacements in the argument list.
  result = newStringOfCap(s.len)
  var i = 0
  var fastChk: set[char] = {}
  for tup in replacements: fastChk.incl(tup[0][0]) # Include first character of all replacements
  while i < s.len:
    block sIteration:
      # Assume most chars in s are not candidates for any replacement operation
      if s[i] in fastChk:
        for tup in replacements:
          if s.continuesWith(tup[0], i):
            add result, tup[1]
            inc(i, tup[0].len)
            break sIteration
      # No matching replacement found
      # copy current character from s
      add result, s[i]
      inc(i)

proc delete*(s: var string, first, last: int) {.noSideEffect,
  rtl, extern: "nsuDelete".} =
  ## Deletes in `s` the characters at position `first` .. `last`.
  ##
  ## This modifies `s` itself, it does not return a copy.
  var i = first
  var j = last+1
  var newLen = len(s)-j+i
  while i < newLen:
    s[i] = s[j]
    inc(i)
    inc(j)
  setLen(s, newLen)

proc toOct*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToOct".} =
  ## Converts `x` into its octal representation.
  ##
  ## The resulting string is always `len` characters long. No leading ``0o``
  ## prefix is generated.
  var
    mask: BiggestInt = 7
    shift: BiggestInt = 0
  assert(len > 0)
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = chr(int((x and mask) shr shift) + ord('0'))
    shift = shift + 3
    mask = mask shl 3

proc toBin*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToBin".} =
  ## Converts `x` into its binary representation.
  ##
  ## The resulting string is always `len` characters long. No leading ``0b``
  ## prefix is generated.
  var
    mask: BiggestInt = 1
    shift: BiggestInt = 0
  assert(len > 0)
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = chr(int((x and mask) shr shift) + ord('0'))
    shift = shift + 1
    mask = mask shl 1

proc insertSep*(s: string, sep = '_', digits = 3): string {.noSideEffect,
  rtl, extern: "nsuInsertSep".} =
  ## Inserts the separator `sep` after `digits` digits from right to left.
  ##
  ## Even though the algorithm works with any string `s`, it is only useful
  ## if `s` contains a number.
  runnableExamples:
    doAssert insertSep("1000000") == "1_000_000"

  var L = (s.len-1) div digits + s.len
  result = newString(L)
  var j = 0
  dec(L)
  for i in countdown(len(s)-1, 0):
    if j == digits:
      result[L] = sep
      dec(L)
      j = 0
    result[L] = s[i]
    inc(j)
    dec(L)

proc escape*(s: string, prefix = "\"", suffix = "\""): string {.noSideEffect,
  rtl, extern: "nsuEscape".} =
  ## Escapes a string `s`. See `system.addEscapedChar <system.html#addEscapedChar>`_
  ## for the escaping scheme.
  ##
  ## The resulting string is prefixed with `prefix` and suffixed with `suffix`.
  ## Both may be empty strings.
  result = newStringOfCap(s.len + s.len shr 2)
  result.add(prefix)
  for c in items(s):
    case c
    of '\0'..'\31', '\127'..'\255':
      add(result, "\\x")
      add(result, toHex(ord(c), 2))
    of '\\': add(result, "\\\\")
    of '\'': add(result, "\\'")
    of '\"': add(result, "\\\"")
    else: add(result, c)
  add(result, suffix)

proc unescape*(s: string, prefix = "\"", suffix = "\""): string {.noSideEffect,
  rtl, extern: "nsuUnescape".} =
  ## Unescapes a string `s`.
  ##
  ## This complements `escape <#escape>`_ as it performs the opposite
  ## operations.
  ##
  ## If `s` does not begin with ``prefix`` and end with ``suffix`` a
  ## ValueError exception will be raised.
  result = newStringOfCap(s.len)
  var i = prefix.len
  if not s.startsWith(prefix):
    raise newException(ValueError,
                       "String does not start with: " & prefix)
  while true:
    if i >= s.len-suffix.len: break
    if s[i] == '\\':
      if i+1 >= s.len:
        result.add('\\')
        break
      case s[i+1]:
      of 'x':
        inc i, 2
        var c: int
        i += parseutils.parseHex(s, c, i, maxLen=2)
        result.add(chr(c))
        dec i, 2
      of '\\':
        result.add('\\')
      of '\'':
        result.add('\'')
      of '\"':
        result.add('\"')
      else:
        result.add("\\" & s[i+1])
      inc(i, 2)
    else:
      result.add(s[i])
      inc(i)
  if not s.endsWith(suffix):
    raise newException(ValueError,
                       "String does not end in: " & suffix)

proc validIdentifier*(s: string): bool {.noSideEffect,
  rtl, extern: "nsuValidIdentifier".} =
  ## Returns true if `s` is a valid identifier.
  ##
  ## A valid identifier starts with a character of the set `IdentStartChars`
  ## and is followed by any number of characters of the set `IdentChars`.
  runnableExamples:
    doAssert "abc_def08".validIdentifier
  if s.len > 0 and s[0] in IdentStartChars:
    for i in 1..s.len-1:
      if s[i] notin IdentChars: return false
    return true

{.push warning[Deprecated]: off.}
proc editDistance*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuEditDistance",
  deprecated: "use editdistance.editDistanceAscii instead".} =
  ## Returns the edit distance between `a` and `b`.
  ##
  ## This uses the `Levenshtein`:idx: distance algorithm with only a linear
  ## memory overhead.
  var len1 = a.len
  var len2 = b.len
  if len1 > len2:
    # make `b` the longer string
    return editDistance(b, a)

  # strip common prefix:
  var s = 0
  while s < len1 and a[s] == b[s]:
    inc(s)
    dec(len1)
    dec(len2)
  # strip common suffix:
  while len1 > 0 and len2 > 0 and a[s+len1-1] == b[s+len2-1]:
    dec(len1)
    dec(len2)
  # trivial cases:
  if len1 == 0: return len2
  if len2 == 0: return len1

  # another special case:
  if len1 == 1:
    for j in s..s+len2-1:
      if a[s] == b[j]: return len2 - 1
    return len2

  inc(len1)
  inc(len2)
  var half = len1 shr 1
  # initalize first row:
  #var row = cast[ptr array[0..high(int) div 8, int]](alloc(len2*sizeof(int)))
  var row: seq[int]
  newSeq(row, len2)
  var e = s + len2 - 1 # end marker
  for i in 1..len2 - half - 1: row[i] = i
  row[0] = len1 - half - 1
  for i in 1 .. len1 - 1:
    var char1 = a[i + s - 1]
    var char2p: int
    var D, x: int
    var p: int
    if i >= len1 - half:
      # skip the upper triangle:
      var offset = i - len1 + half
      char2p = offset
      p = offset
      var c3 = row[p] + ord(char1 != b[s + char2p])
      inc(p)
      inc(char2p)
      x = row[p] + 1
      D = x
      if x > c3: x = c3
      row[p] = x
      inc(p)
    else:
      p = 1
      char2p = 0
      D = i
      x = i
    if i <= half + 1:
      # skip the lower triangle:
      e = len2 + i - half - 2
    # main:
    while p <= e:
      dec(D)
      var c3 = D + ord(char1 != b[char2p + s])
      inc(char2p)
      inc(x)
      if x > c3: x = c3
      D = row[p] + 1
      if x > D: x = D
      row[p] = x
      inc(p)
    # lower triangle sentinel:
    if i <= half:
      dec(D)
      var c3 = D + ord(char1 != b[char2p + s])
      inc(x)
      if x > c3: x = c3
      row[p] = x
  result = row[e]
{.pop.}

# floating point formating:
when not defined(js):
  proc c_sprintf(buf, frmt: cstring): cint {.header: "<stdio.h>",
                                     importc: "sprintf", varargs, noSideEffect.}

type
  FloatFormatMode* = enum ## the different modes of floating point formating
    ffDefault,         ## use the shorter floating point notation
    ffDecimal,         ## use decimal floating point notation
    ffScientific       ## use scientific notation (using ``e`` character)

{.deprecated: [TFloatFormat: FloatFormatMode].}

proc formatBiggestFloat*(f: BiggestFloat, format: FloatFormatMode = ffDefault,
                         precision: range[-1..32] = 16;
                         decimalSep = '.'): string {.
                         noSideEffect, rtl, extern: "nsu$1".} =
  ## Converts a floating point value `f` to a string.
  ##
  ## If ``format == ffDecimal`` then precision is the number of digits to
  ## be printed after the decimal point.
  ## If ``format == ffScientific`` then precision is the maximum number
  ## of significant digits to be printed.
  ## `precision`'s default value is the maximum number of meaningful digits
  ## after the decimal point for Nim's ``biggestFloat`` type.
  ##
  ## If ``precision == -1``, it tries to format it nicely.
  when defined(js):
    var precision = precision
    if precision == -1:
      # use the same default precision as c_sprintf
      precision = 6
    var res: cstring
    case format
    of ffDefault:
      {.emit: "`res` = `f`.toString();".}
    of ffDecimal:
      {.emit: "`res` = `f`.toFixed(`precision`);".}
    of ffScientific:
      {.emit: "`res` = `f`.toExponential(`precision`);".}
    result = $res
    if 1.0 / f == -Inf:
      # JavaScript removes the "-" from negative Zero, add it back here
      result = "-" & $res
    for i in 0 ..< result.len:
      # Depending on the locale either dot or comma is produced,
      # but nothing else is possible:
      if result[i] in {'.', ','}: result[i] = decimalsep
  else:
    const floatFormatToChar: array[FloatFormatMode, char] = ['g', 'f', 'e']
    var
      frmtstr {.noinit.}: array[0..5, char]
      buf {.noinit.}: array[0..2500, char]
      L: cint
    frmtstr[0] = '%'
    if precision >= 0:
      frmtstr[1] = '#'
      frmtstr[2] = '.'
      frmtstr[3] = '*'
      frmtstr[4] = floatFormatToChar[format]
      frmtstr[5] = '\0'
      when defined(nimNoArrayToCstringConversion):
        L = c_sprintf(addr buf, addr frmtstr, precision, f)
      else:
        L = c_sprintf(buf, frmtstr, precision, f)
    else:
      frmtstr[1] = floatFormatToChar[format]
      frmtstr[2] = '\0'
      when defined(nimNoArrayToCstringConversion):
        L = c_sprintf(addr buf, addr frmtstr, f)
      else:
        L = c_sprintf(buf, frmtstr, f)
    result = newString(L)
    for i in 0 ..< L:
      # Depending on the locale either dot or comma is produced,
      # but nothing else is possible:
      if buf[i] in {'.', ','}: result[i] = decimalsep
      else: result[i] = buf[i]
    when defined(windows):
      # VS pre 2015 violates the C standard: "The exponent always contains at
      # least two digits, and only as many more digits as necessary to
      # represent the exponent." [C11 §7.21.6.1]
      # The following post-processing fixes this behavior.
      if result.len > 4 and result[^4] == '+' and result[^3] == '0':
        result[^3] = result[^2]
        result[^2] = result[^1]
        result.setLen(result.len - 1)

proc formatFloat*(f: float, format: FloatFormatMode = ffDefault,
                  precision: range[-1..32] = 16; decimalSep = '.'): string {.
                  noSideEffect, rtl, extern: "nsu$1".} =
  ## Converts a floating point value `f` to a string.
  ##
  ## If ``format == ffDecimal`` then precision is the number of digits to
  ## be printed after the decimal point.
  ## If ``format == ffScientific`` then precision is the maximum number
  ## of significant digits to be printed.
  ## `precision`'s default value is the maximum number of meaningful digits
  ## after the decimal point for Nim's ``float`` type.
  ##
  ## If ``precision == -1``, it tries to format it nicely.
  runnableExamples:
    let x = 123.456
    doAssert x.formatFloat() == "123.4560000000000"
    doAssert x.formatFloat(ffDecimal, 4) == "123.4560"
    doAssert x.formatFloat(ffScientific, 2) == "1.23e+02"
  result = formatBiggestFloat(f, format, precision, decimalSep)

proc trimZeros*(x: var string) {.noSideEffect.} =
  ## Trim trailing zeros from a formatted floating point
  ## value (`x`).  Modifies the passed value.
  var spl: seq[string]
  if x.contains('.') or x.contains(','):
    if x.contains('e'):
      spl = x.split('e')
      x = spl[0]
    while x[x.high] == '0':
      x.setLen(x.len-1)
    if x[x.high] in [',', '.']:
      x.setLen(x.len-1)
    if spl.len > 0:
      x &= "e" & spl[1]

type
  BinaryPrefixMode* = enum ## the different names for binary prefixes
    bpIEC, # use the IEC/ISO standard prefixes such as kibi
    bpColloquial # use the colloquial kilo, mega etc

proc formatSize*(bytes: int64,
                 decimalSep = '.',
                 prefix = bpIEC,
                 includeSpace = false): string {.noSideEffect.} =
  ## Rounds and formats `bytes`.
  ##
  ## By default, uses the IEC/ISO standard binary prefixes, so 1024 will be
  ## formatted as 1KiB.  Set prefix to `bpColloquial` to use the colloquial
  ## names from the SI standard (e.g. k for 1000 being reused as 1024).
  ##
  ## `includeSpace` can be set to true to include the (SI preferred) space
  ## between the number and the unit (e.g. 1 KiB).
  runnableExamples:
    doAssert formatSize((1'i64 shl 31) + (300'i64 shl 20)) == "2.293GiB"
    doAssert formatSize((2.234*1024*1024).int) == "2.234MiB"
    doAssert formatSize(4096, includeSpace=true) == "4 KiB"
    doAssert formatSize(4096, prefix=bpColloquial, includeSpace=true) == "4 kB"
    doAssert formatSize(4096) == "4KiB"
    doAssert formatSize(5_378_934, prefix=bpColloquial, decimalSep=',') == "5,13MB"
  const iecPrefixes = ["", "Ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi"]
  const collPrefixes = ["", "k", "M", "G", "T", "P", "E", "Z", "Y"]
  var
    xb: int64 = bytes
    fbytes: float
    last_xb: int64 = bytes
    matchedIndex: int
    prefixes: array[9, string]
  if prefix == bpColloquial:
    prefixes = collPrefixes
  else:
    prefixes = iecPrefixes

  # Iterate through prefixes seeing if value will be greater than
  # 0 in each case
  for index in 1..<prefixes.len:
    last_xb = xb
    xb = bytes div (1'i64 shl (index*10))
    matchedIndex = index
    if xb == 0:
      xb = last_xb
      matchedIndex = index - 1
      break
  # xb has the integer number for the latest value; index should be correct
  fbytes = bytes.float / (1'i64 shl (matchedIndex*10)).float
  result = formatFloat(fbytes, format=ffDecimal, precision=3, decimalSep=decimalSep)
  result.trimZeros()
  if includeSpace:
    result &= " "
  result &= prefixes[matchedIndex]
  result &= "B"

proc formatEng*(f: BiggestFloat,
                precision: range[0..32] = 10,
                trim: bool = true,
                siPrefix: bool = false,
                unit: string = "",
                decimalSep = '.',
                useUnitSpace = false): string {.noSideEffect.} =
  ## Converts a floating point value `f` to a string using engineering notation.
  ##
  ## Numbers in of the range -1000.0<f<1000.0 will be formatted without an
  ## exponent. Numbers outside of this range will be formatted as a
  ## significand in the range -1000.0<f<1000.0 and an exponent that will always
  ## be an integer multiple of 3, corresponding with the SI prefix scale k, M,
  ## G, T etc for numbers with an absolute value greater than 1 and m, μ, n, p
  ## etc for numbers with an absolute value less than 1.
  ##
  ## The default configuration (`trim=true` and `precision=10`) shows the
  ## **shortest** form that precisely (up to a maximum of 10 decimal places)
  ## displays the value. For example, 4.100000 will be displayed as 4.1 (which
  ## is mathematically identical) whereas 4.1000003 will be displayed as
  ## 4.1000003.
  ##
  ## If `trim` is set to true, trailing zeros will be removed; if false, the
  ## number of digits specified by `precision` will always be shown.
  ##
  ## `precision` can be used to set the number of digits to be shown after the
  ## decimal point or (if `trim` is true) the maximum number of digits to be
  ## shown.
  ##
  ## .. code-block:: nim
  ##
  ##    formatEng(0, 2, trim=false) == "0.00"
  ##    formatEng(0, 2) == "0"
  ##    formatEng(0.053, 0) == "53e-3"
  ##    formatEng(52731234, 2) == "52.73e6"
  ##    formatEng(-52731234, 2) == "-52.73e6"
  ##
  ## If `siPrefix` is set to true, the number will be displayed with the SI
  ## prefix corresponding to the exponent. For example 4100 will be displayed
  ## as "4.1 k" instead of "4.1e3". Note that `u` is used for micro- in place
  ## of the greek letter mu (μ) as per ISO 2955. Numbers with an absolute
  ## value outside of the range 1e-18<f<1000e18 (1a<f<1000E) will be displayed
  ## with an exponent rather than an SI prefix, regardless of whether
  ## `siPrefix` is true.
  ##
  ## If `useUnitSpace` is true, the provided unit will be appended to the string
  ## (with a space as required by the SI standard). This behaviour is slightly
  ## different to appending the unit to the result as the location of the space
  ## is altered depending on whether there is an exponent.
  ##
  ## .. code-block:: nim
  ##
  ##    formatEng(4100, siPrefix=true, unit="V") == "4.1 kV"
  ##    formatEng(4.1, siPrefix=true, unit="V") == "4.1 V"
  ##    formatEng(4.1, siPrefix=true) == "4.1" # Note lack of space
  ##    formatEng(4100, siPrefix=true) == "4.1 k"
  ##    formatEng(4.1, siPrefix=true, unit="") == "4.1 " # Space with unit=""
  ##    formatEng(4100, siPrefix=true, unit="") == "4.1 k"
  ##    formatEng(4100) == "4.1e3"
  ##    formatEng(4100, unit="V") == "4.1e3 V"
  ##    formatEng(4100, unit="", useUnitSpace=true) == "4.1e3 " # Space with useUnitSpace=true
  ##
  ## `decimalSep` is used as the decimal separator.
  var
    absolute: BiggestFloat
    significand: BiggestFloat
    fexponent: BiggestFloat
    exponent: int
    splitResult: seq[string]
    suffix: string = ""
  proc getPrefix(exp: int): char =
    ## Get the SI prefix for a given exponent
    ##
    ## Assumes exponent is a multiple of 3; returns ' ' if no prefix found
    const siPrefixes = ['a','f','p','n','u','m',' ','k','M','G','T','P','E']
    var index: int = (exp div 3) + 6
    result = ' '
    if index in low(siPrefixes)..high(siPrefixes):
      result = siPrefixes[index]

  # Most of the work is done with the sign ignored, so get the absolute value
  absolute = abs(f)
  significand = f

  if absolute == 0.0:
    # Simple case: just format it and force the exponent to 0
    exponent = 0
    result = significand.formatBiggestFloat(ffDecimal, precision, decimalSep='.')
  else:
    # Find the best exponent that's a multiple of 3
    fexponent = floor(log10(absolute))
    fexponent = 3.0 * floor(fexponent / 3.0)
    # Adjust the significand for the new exponent
    significand /= pow(10.0, fexponent)

    # Adjust the significand and check whether it has affected
    # the exponent
    absolute = abs(significand)
    if absolute >= 1000.0:
      significand *= 0.001
      fexponent += 3
    # Components of the result:
    result = significand.formatBiggestFloat(ffDecimal, precision, decimalSep='.')
    exponent = fexponent.int()

  splitResult = result.split('.')
  result = splitResult[0]
  # result should have at most one decimal character
  if splitResult.len() > 1:
    # If trim is set, we get rid of trailing zeros.  Don't use trimZeros here as
    # we can be a bit more efficient through knowledge that there will never be
    # an exponent in this part.
    if trim:
        while splitResult[1].endsWith("0"):
          # Trim last character
          splitResult[1].setLen(splitResult[1].len-1)
        if splitResult[1].len() > 0:
          result &= decimalSep & splitResult[1]
    else:
      result &= decimalSep & splitResult[1]

  # Combine the results accordingly
  if siPrefix and exponent != 0:
    var p = getPrefix(exponent)
    if p != ' ':
      suffix = " " & p
      exponent = 0 # Exponent replaced by SI prefix
  if suffix == "" and useUnitSpace:
    suffix = " "
  suffix &= unit
  if exponent != 0:
    result &= "e" & $exponent
  result &= suffix

proc findNormalized(x: string, inArray: openArray[string]): int =
  var i = 0
  while i < high(inArray):
    if cmpIgnoreStyle(x, inArray[i]) == 0: return i
    inc(i, 2) # incrementing by 1 would probably lead to a
              # security hole...
  return -1

proc invalidFormatString() {.noinline.} =
  raise newException(ValueError, "invalid format string")

proc addf*(s: var string, formatstr: string, a: varargs[string, `$`]) {.
  noSideEffect, rtl, extern: "nsuAddf".} =
  ## The same as ``add(s, formatstr % a)``, but more efficient.
  const PatternChars = {'a'..'z', 'A'..'Z', '0'..'9', '\128'..'\255', '_'}
  var i = 0
  var num = 0
  while i < len(formatstr):
    if formatstr[i] == '$' and i+1 < len(formatstr):
      case formatstr[i+1]
      of '#':
        if num > a.high: invalidFormatString()
        add s, a[num]
        inc i, 2
        inc num
      of '$':
        add s, '$'
        inc(i, 2)
      of '1'..'9', '-':
        var j = 0
        inc(i) # skip $
        var negative = formatstr[i] == '-'
        if negative: inc i
        while i < formatstr.len and formatstr[i] in Digits:
          j = j * 10 + ord(formatstr[i]) - ord('0')
          inc(i)
        let idx = if not negative: j-1 else: a.len-j
        if idx < 0 or idx > a.high: invalidFormatString()
        add s, a[idx]
      of '{':
        var j = i+2
        var k = 0
        var negative = formatstr[j] == '-'
        if negative: inc j
        var isNumber = 0
        while j < formatstr.len and formatstr[j] notin {'\0', '}'}:
          if formatstr[j] in Digits:
            k = k * 10 + ord(formatstr[j]) - ord('0')
            if isNumber == 0: isNumber = 1
          else:
            isNumber = -1
          inc(j)
        if isNumber == 1:
          let idx = if not negative: k-1 else: a.len-k
          if idx < 0 or idx > a.high: invalidFormatString()
          add s, a[idx]
        else:
          var x = findNormalized(substr(formatstr, i+2, j-1), a)
          if x >= 0 and x < high(a): add s, a[x+1]
          else: invalidFormatString()
        i = j+1
      of 'a'..'z', 'A'..'Z', '\128'..'\255', '_':
        var j = i+1
        while j < formatstr.len and formatstr[j] in PatternChars: inc(j)
        var x = findNormalized(substr(formatstr, i+1, j-1), a)
        if x >= 0 and x < high(a): add s, a[x+1]
        else: invalidFormatString()
        i = j
      else:
        invalidFormatString()
    else:
      add s, formatstr[i]
      inc(i)

proc `%` *(formatstr: string, a: openArray[string]): string {.noSideEffect,
  rtl, extern: "nsuFormatOpenArray".} =
  ## Interpolates a format string with the values from `a`.
  ##
  ## The `substitution`:idx: operator performs string substitutions in
  ## `formatstr` and returns a modified `formatstr`. This is often called
  ## `string interpolation`:idx:.
  ##
  ## This is best explained by an example:
  ##
  ## .. code-block:: nim
  ##   "$1 eats $2." % ["The cat", "fish"]
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "The cat eats fish."
  ##
  ## The substitution variables (the thing after the ``$``) are enumerated
  ## from 1 to ``a.len``.
  ## To produce a verbatim ``$``, use ``$$``.
  ## The notation ``$#`` can be used to refer to the next substitution
  ## variable:
  ##
  ## .. code-block:: nim
  ##   "$# eats $#." % ["The cat", "fish"]
  ##
  ## Substitution variables can also be words (that is
  ## ``[A-Za-z_]+[A-Za-z0-9_]*``) in which case the arguments in `a` with even
  ## indices are keys and with odd indices are the corresponding values.
  ## An example:
  ##
  ## .. code-block:: nim
  ##   "$animal eats $food." % ["animal", "The cat", "food", "fish"]
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "The cat eats fish."
  ##
  ## The variables are compared with `cmpIgnoreStyle`. `ValueError` is
  ## raised if an ill-formed format string has been passed to the `%` operator.
  result = newStringOfCap(formatstr.len + a.len shl 4)
  addf(result, formatstr, a)

proc `%` *(formatstr, a: string): string {.noSideEffect,
  rtl, extern: "nsuFormatSingleElem".} =
  ## This is the same as ``formatstr % [a]``.
  result = newStringOfCap(formatstr.len + a.len)
  addf(result, formatstr, [a])

proc format*(formatstr: string, a: varargs[string, `$`]): string {.noSideEffect,
  rtl, extern: "nsuFormatVarargs".} =
  ## This is the same as ``formatstr % a`` except that it supports
  ## auto stringification.
  result = newStringOfCap(formatstr.len + a.len)
  addf(result, formatstr, a)

{.pop.}

proc removeSuffix*(s: var string, chars: set[char] = Newlines) {.
  rtl, extern: "nsuRemoveSuffixCharSet".} =
  ## Removes all characters from `chars` from the end of the string `s`
  ## (in-place).
  runnableExamples:
     var userInput = "Hello World!*~\r\n"
     userInput.removeSuffix
     doAssert userInput == "Hello World!*~"
     userInput.removeSuffix({'~', '*'})
     doAssert userInput == "Hello World!"

     var otherInput = "Hello!?!"
     otherInput.removeSuffix({'!', '?'})
     doAssert otherInput == "Hello"
  if s.len == 0: return
  var last = s.high
  while last > -1 and s[last] in chars: last -= 1
  s.setLen(last + 1)

proc removeSuffix*(s: var string, c: char) {.
  rtl, extern: "nsuRemoveSuffixChar".} =
  ## Removes all occurrences of a single character (in-place) from the end
  ## of a string.
  ##
  runnableExamples:
     var table = "users"
     table.removeSuffix('s')
     doAssert table == "user"

     var dots = "Trailing dots......."
     dots.removeSuffix('.')
     doAssert dots == "Trailing dots"
  removeSuffix(s, chars = {c})

proc removeSuffix*(s: var string, suffix: string) {.
  rtl, extern: "nsuRemoveSuffixString".} =
  ## Remove the first matching suffix (in-place) from a string.
  runnableExamples:
     var answers = "yeses"
     answers.removeSuffix("es")
     doAssert answers == "yes"
  var newLen = s.len
  if s.endsWith(suffix):
    newLen -= len(suffix)
    s.setLen(newLen)

proc removePrefix*(s: var string, chars: set[char] = Newlines) {.
  rtl, extern: "nsuRemovePrefixCharSet".} =
  ## Removes all characters from `chars` from the start of the string `s`
  ## (in-place).
  ##
  runnableExamples:
     var userInput = "\r\n*~Hello World!"
     userInput.removePrefix
     doAssert userInput == "*~Hello World!"
     userInput.removePrefix({'~', '*'})
     doAssert userInput == "Hello World!"

     var otherInput = "?!?Hello!?!"
     otherInput.removePrefix({'!', '?'})
     doAssert otherInput == "Hello!?!"
  var start = 0
  while start < s.len and s[start] in chars: start += 1
  if start > 0: s.delete(0, start - 1)

proc removePrefix*(s: var string, c: char) {.
  rtl, extern: "nsuRemovePrefixChar".} =
  ## Removes all occurrences of a single character (in-place) from the start
  ## of a string.
  ##
  runnableExamples:
     var ident = "pControl"
     ident.removePrefix('p')
     doAssert ident == "Control"
  removePrefix(s, chars = {c})

proc removePrefix*(s: var string, prefix: string) {.
  rtl, extern: "nsuRemovePrefixString".} =
  ## Remove the first matching prefix (in-place) from a string.
  ##
  runnableExamples:
     var answers = "yesyes"
     answers.removePrefix("yes")
     doAssert answers == "yes"
  if s.startsWith(prefix):
    s.delete(0, prefix.len - 1)

proc stripLineEnd*(s: var string) =
  ## Returns ``s`` stripped from one of these suffixes:
  ## ``\r, \n, \r\n, \f, \v`` (at most once instance).
  ## For example, can be useful in conjunction with ``osproc.execCmdEx``.
  runnableExamples:
    var s = "foo\n\n"
    s.stripLineEnd
    doAssert s == "foo\n"
    s = "foo\r\n"
    s.stripLineEnd
    doAssert s == "foo"
  if s.len > 0:
    case s[^1]
    of '\n':
      if s.len > 1 and s[^2] == '\r':
        s.setLen s.len-2
      else:
        s.setLen s.len-1
    of '\r', '\v', '\f':
      s.setLen s.len-1
    else:
      discard

when isMainModule:
  proc nonStaticTests =
    doAssert formatBiggestFloat(1234.567, ffDecimal, -1) == "1234.567000"
    when not defined(js):
      doAssert formatBiggestFloat(1234.567, ffDecimal, 0) == "1235."           # <=== bug 8242
    doAssert formatBiggestFloat(1234.567, ffDecimal, 1) == "1234.6"
    doAssert formatBiggestFloat(0.00000000001, ffDecimal, 11) == "0.00000000001"
    doAssert formatBiggestFloat(0.00000000001, ffScientific, 1, ',') in
                                                     ["1,0e-11", "1,0e-011"]
    # bug #6589
    when not defined(js):
      doAssert formatFloat(123.456, ffScientific, precision = -1) == "1.234560e+02"

    doAssert "$# $3 $# $#" % ["a", "b", "c"] == "a c b c"
    doAssert "${1}12 ${-1}$2" % ["a", "b"] == "a12 bb"

    block: # formatSize tests
      when not defined(js):
        doAssert formatSize((1'i64 shl 31) + (300'i64 shl 20)) == "2.293GiB"   # <=== bug #8231
      doAssert formatSize((2.234*1024*1024).int) == "2.234MiB"
      doAssert formatSize(4096) == "4KiB"
      doAssert formatSize(4096, prefix=bpColloquial, includeSpace=true) == "4 kB"
      doAssert formatSize(4096, includeSpace=true) == "4 KiB"
      doAssert formatSize(5_378_934, prefix=bpColloquial, decimalSep=',') == "5,13MB"

    block: # formatEng tests
      doAssert formatEng(0, 2, trim=false) == "0.00"
      doAssert formatEng(0, 2) == "0"
      doAssert formatEng(53, 2, trim=false) == "53.00"
      doAssert formatEng(0.053, 2, trim=false) == "53.00e-3"
      doAssert formatEng(0.053, 4, trim=false) == "53.0000e-3"
      doAssert formatEng(0.053, 4, trim=true) == "53e-3"
      doAssert formatEng(0.053, 0) == "53e-3"
      doAssert formatEng(52731234) == "52.731234e6"
      doAssert formatEng(-52731234) == "-52.731234e6"
      doAssert formatEng(52731234, 1) == "52.7e6"
      doAssert formatEng(-52731234, 1) == "-52.7e6"
      doAssert formatEng(52731234, 1, decimalSep=',') == "52,7e6"
      doAssert formatEng(-52731234, 1, decimalSep=',') == "-52,7e6"

      doAssert formatEng(4100, siPrefix=true, unit="V") == "4.1 kV"
      doAssert formatEng(4.1, siPrefix=true, unit="V", useUnitSpace=true) == "4.1 V"
      doAssert formatEng(4.1, siPrefix=true) == "4.1" # Note lack of space
      doAssert formatEng(4100, siPrefix=true) == "4.1 k"
      doAssert formatEng(4.1, siPrefix=true, unit="", useUnitSpace=true) == "4.1 " # Includes space
      doAssert formatEng(4100, siPrefix=true, unit="") == "4.1 k"
      doAssert formatEng(4100) == "4.1e3"
      doAssert formatEng(4100, unit="V", useUnitSpace=true) == "4.1e3 V"
      doAssert formatEng(4100, unit="", useUnitSpace=true) == "4.1e3 "
      # Don't use SI prefix as number is too big
      doAssert formatEng(3.1e22, siPrefix=true, unit="a", useUnitSpace=true) == "31e21 a"
      # Don't use SI prefix as number is too small
      doAssert formatEng(3.1e-25, siPrefix=true, unit="A", useUnitSpace=true) == "310e-27 A"

  proc staticTests =
    doAssert align("abc", 4) == " abc"
    doAssert align("a", 0) == "a"
    doAssert align("1232", 6) == "  1232"
    doAssert align("1232", 6, '#') == "##1232"

    doAssert alignLeft("abc", 4) == "abc "
    doAssert alignLeft("a", 0) == "a"
    doAssert alignLeft("1232", 6) == "1232  "
    doAssert alignLeft("1232", 6, '#') == "1232##"

    let
      inp = """ this is a long text --  muchlongerthan10chars and here
                 it goes"""
      outp = " this is a\nlong text\n--\nmuchlongerthan10chars\nand here\nit goes"
    doAssert wordWrap(inp, 10, false) == outp

    let
      longInp = """ThisIsOneVeryLongStringWhichWeWillSplitIntoEightSeparatePartsNow"""
      longOutp = "ThisIsOn\neVeryLon\ngStringW\nhichWeWi\nllSplitI\nntoEight\nSeparate\nPartsNow"
    doAssert wordWrap(longInp, 8, true) == longOutp

    doAssert "$animal eats $food." % ["animal", "The cat", "food", "fish"] ==
             "The cat eats fish."

    doAssert "-ld a-ldz -ld".replaceWord("-ld") == " a-ldz "
    doAssert "-lda-ldz -ld abc".replaceWord("-ld") == "-lda-ldz  abc"

    doAssert "-lda-ldz -ld abc".replaceWord("") == "-lda-ldz -ld abc"
    doAssert "oo".replace("", "abc") == "abcoabcoabc"

    type MyEnum = enum enA, enB, enC, enuD, enE
    doAssert parseEnum[MyEnum]("enu_D") == enuD

    doAssert parseEnum("invalid enum value", enC) == enC

    doAssert center("foo", 13) == "     foo     "
    doAssert center("foo", 0) == "foo"
    doAssert center("foo", 3, fillChar = 'a') == "foo"
    doAssert center("foo", 10, fillChar = '\t') == "\t\t\tfoo\t\t\t\t"

    doAssert count("foofoofoo", "foofoo") == 1
    doAssert count("foofoofoo", "foofoo", overlapping = true) == 2
    doAssert count("foofoofoo", 'f') == 3
    doAssert count("foofoofoobar", {'f','b'}) == 4

    doAssert strip("  foofoofoo  ") == "foofoofoo"
    doAssert strip("sfoofoofoos", chars = {'s'}) == "foofoofoo"
    doAssert strip("barfoofoofoobar", chars = {'b', 'a', 'r'}) == "foofoofoo"
    doAssert strip("stripme but don't strip this stripme",
                   chars = {'s', 't', 'r', 'i', 'p', 'm', 'e'}) ==
                   " but don't strip this "
    doAssert strip("sfoofoofoos", leading = false, chars = {'s'}) == "sfoofoofoo"
    doAssert strip("sfoofoofoos", trailing = false, chars = {'s'}) == "foofoofoos"

    doAssert "  foo\n  bar".indent(4, "Q") == "QQQQ  foo\nQQQQ  bar"

    doAssert "abba".multiReplace(("a", "b"), ("b", "a")) == "baab"
    doAssert "Hello World.".multiReplace(("ello", "ELLO"), ("World.", "PEOPLE!")) == "HELLO PEOPLE!"
    doAssert "aaaa".multiReplace(("a", "aa"), ("aa", "bb")) == "aaaaaaaa"

    doAssert isAlphaAscii('r')
    doAssert isAlphaAscii('A')
    doAssert(not isAlphaAscii('$'))

    doAssert isAlphaNumeric('3')
    doAssert isAlphaNumeric('R')
    doAssert(not isAlphaNumeric('!'))

    doAssert isDigit('3')
    doAssert(not isDigit('a'))
    doAssert(not isDigit('%'))

    doAssert isSpaceAscii('\t')
    doAssert isSpaceAscii('\l')
    doAssert(not isSpaceAscii('A'))

    doAssert(isNilOrWhitespace(""))
    doAssert(isNilOrWhitespace("       "))
    doAssert(isNilOrWhitespace("\t\l \v\r\f"))
    doAssert(not isNilOrWhitespace("ABc   \td"))

    doAssert isLowerAscii('a')
    doAssert isLowerAscii('z')
    doAssert(not isLowerAscii('A'))
    doAssert(not isLowerAscii('5'))
    doAssert(not isLowerAscii('&'))
    doAssert(not isLowerAscii(' '))

    doAssert isUpperAscii('A')
    doAssert(not isUpperAscii('b'))
    doAssert(not isUpperAscii('5'))
    doAssert(not isUpperAscii('%'))

    doAssert rsplit("foo bar", seps=Whitespace) == @["foo", "bar"]
    doAssert rsplit(" foo bar", seps=Whitespace, maxsplit=1) == @[" foo", "bar"]
    doAssert rsplit(" foo bar ", seps=Whitespace, maxsplit=1) == @[" foo bar", ""]
    doAssert rsplit(":foo:bar", sep=':') == @["", "foo", "bar"]
    doAssert rsplit(":foo:bar", sep=':', maxsplit=2) == @["", "foo", "bar"]
    doAssert rsplit(":foo:bar", sep=':', maxsplit=3) == @["", "foo", "bar"]
    doAssert rsplit("foothebar", sep="the") == @["foo", "bar"]

    doAssert(unescape(r"\x013", "", "") == "\x013")

    doAssert join(["foo", "bar", "baz"]) == "foobarbaz"
    doAssert join(@["foo", "bar", "baz"], ", ") == "foo, bar, baz"
    doAssert join([1, 2, 3]) == "123"
    doAssert join(@[1, 2, 3], ", ") == "1, 2, 3"

    doAssert """~~!!foo
~~!!bar
~~!!baz""".unindent(2, "~~!!") == "foo\nbar\nbaz"

    doAssert """~~!!foo
~~!!bar
~~!!baz""".unindent(2, "~~!!aa") == "~~!!foo\n~~!!bar\n~~!!baz"
    doAssert """~~foo
~~  bar
~~  baz""".unindent(4, "~") == "foo\n  bar\n  baz"
    doAssert """foo
bar
    baz
  """.unindent(4) == "foo\nbar\nbaz\n"
    doAssert """foo
    bar
    baz
  """.unindent(2) == "foo\n  bar\n  baz\n"
    doAssert """foo
    bar
    baz
  """.unindent(100) == "foo\nbar\nbaz\n"

    doAssert """foo
    foo
    bar
  """.unindent() == "foo\nfoo\nbar\n"

    let s = " this is an example  "
    let s2 = ":this;is;an:example;;"

    doAssert s.split() == @["", "this", "is", "an", "example", "", ""]
    doAssert s2.split(seps={':', ';'}) == @["", "this", "is", "an", "example", "", ""]
    doAssert s.split(maxsplit=4) == @["", "this", "is", "an", "example  "]
    doAssert s.split(' ', maxsplit=1) == @["", "this is an example  "]
    doAssert s.split(" ", maxsplit=4) == @["", "this", "is", "an", "example  "]

    doAssert s.splitWhitespace() == @["this", "is", "an", "example"]
    doAssert s.splitWhitespace(maxsplit=1) == @["this", "is an example  "]
    doAssert s.splitWhitespace(maxsplit=2) == @["this", "is", "an example  "]
    doAssert s.splitWhitespace(maxsplit=3) == @["this", "is", "an", "example  "]
    doAssert s.splitWhitespace(maxsplit=4) == @["this", "is", "an", "example"]

    block: # startsWith / endsWith char tests
      var s = "abcdef"
      doAssert s.startsWith('a')
      doAssert s.startsWith('b') == false
      doAssert s.endsWith('f')
      doAssert s.endsWith('a') == false
      doAssert s.endsWith('\0') == false

    #echo("strutils tests passed")

  nonStaticTests()
  staticTests()
  static: staticTests()