#lang mzscheme

(require scheme/contract)

(require (file "base.ss"))

; Procedures -----------------------------------

(define (symbol-or-false? value)
  (or (symbol? value)
      (eq? value #f)))

(define (string-or-false? value)
  (or (string? value)
      (eq? value #f)))

(define (number-or-false? value)
  (or (number? value)
      (eq? value #f)))

(define (integer-or-false? value)
  (or (integer? value)
      (eq? value #f)))

; Custom contracts -----------------------------

(define (arity/c num-args)
  (lambda (proc)
    (and (procedure? proc)
         (procedure-arity-includes? proc num-args))))

; Provide statements ---------------------------

(provide symbol-or-false?
         string-or-false?
         number-or-false?
         integer-or-false?
         arity/c)