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- (defmacro whenx (cond exp . rest)
- `(if ,cond
- (begin ,exp . ,rest)))
- (define-for-syntax (alter-syntax-datum proc stx)
- (datum->syntax-object stx (proc (syntax-object->datum stx))))
- (define-syntax define-symbol-altering-macro
- (syntax-rules ()
- ((_ (macro-name arg) expr . exprs)
- (define-symbol-altering-macro macro-name (lambda (arg) expr . exprs)))
- ((_ macro-name proc)
- (define-syntax macro-name
- (lambda (stx)
- (syntax-case stx ()
- ((_ sym . args)
- (let ((new-sym (alter-syntax-datum proc (syntax sym))))
- #`(#,new-sym . args)))))))))
- (define-symbol-altering-macro (call-reversename sym)
- (string->symbol ;; OK: lambda2 BAD: lambda3
- (list->string
- (reverse
- (string->list
- (symbol->string sym))))))
- (display (call-reversename xam 3 2 7 6)) (newline)
- ;; Output: 7
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