struct/con

struct_con.rkt

(require (for-syntax syntax/parse))

(define-syntax (struct/con stx)
  (syntax-parse stx 
    [(_ id ((pa colon checkers) ... ))
     #:when (and (map (lambda (x) (eqv? (syntax-e #'x) ':)) (syntax->datum #'(colon ...))))
     (begin
       (define make-id (string->symbol (string-append "make-" (symbol->string (syntax->datum  #'id)))))              
        #`(begin                  
         (define-struct id (pa ...))
         (define old-make #,make-id)
         (define (check-fn p checker) (unless (checker p) (error 'arguments "~a is not a valid parameter for \"~a\" struct" p (syntax-e #'id))))         
         (set! #,make-id
               (lambda (pa ...)
                 (begin 
                   ((lambda (pa ...)
                     (begin (check-fn pa checkers) ...)) pa ...)
                   (old-make pa ...)
                   )))))]))