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- The set type models the mathematical notion of a set. The set's basetype can
- only be an ordinal type of a certain size, namely:
- * ``int8``-``int16``
- * ``uint8``/``byte``-``uint16``
- * ``char``
- * ``enum``
- or equivalent. The reason is that sets are implemented as high
- performance bit vectors. Attempting to declare a set with a larger type will
- result in an error:
- .. code-block:: nim
- var s: set[int64] # Error: set is too large
- Sets can be constructed via the set constructor: ``{}`` is the empty set. The
- empty set is type compatible with any concrete set type. The constructor
- can also be used to include elements (and ranges of elements):
- .. code-block:: nim
- type
- CharSet = set[char]
- var
- x: CharSet
- x = {'a'..'z', '0'..'9'} # This constructs a set that contains the
- # letters from 'a' to 'z' and the digits
- # from '0' to '9'
- These operations are supported by sets:
- ================== ========================================================
- operation meaning
- ================== ========================================================
- ``A + B`` union of two sets
- ``A * B`` intersection of two sets
- ``A - B`` difference of two sets (A without B's elements)
- ``A == B`` set equality
- ``A <= B`` subset relation (A is subset of B or equal to B)
- ``A < B`` strong subset relation (A is a real subset of B)
- ``e in A`` set membership (A contains element e)
- ``e notin A`` A does not contain element e
- ``contains(A, e)`` A contains element e
- ``card(A)`` the cardinality of A (number of elements in A)
- ``incl(A, elem)`` same as ``A = A + {elem}``
- ``excl(A, elem)`` same as ``A = A - {elem}``
- ================== ========================================================
- Sets are often used to define a type for the *flags* of a procedure. This is
- a much cleaner (and type safe) solution than just defining integer
- constants that should be ``or``'ed together.
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