;;; Random useful utilities.
;;; Excerpted from SCSH
;;; Copyright (c) 1993 Olin Shivers

(define-module (scsh utilities)
  #:export (check-arg
	    stringify
	    loophole))

;;; From guile-scsh/loophole.scm
;;; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees.  See file COPYING.
;;; original file: alt/loophole.scm.
(define-syntax loophole
  (syntax-rules ()
    ((loophole ?type ?form)
     (begin (lambda () ?type)    ;Elicit unbound-variable warnings, etc.
	    ?form))))

;;; We loophole the call to ERROR -- the point is that perhaps the
;;; user will interact with a breakpoint, and proceed with a new
;;; value, which we will then pass to a new invocation of CHECK-ARG
;;; for approval.
(define (check-arg pred val caller)
  (if (pred val) val
      (check-arg pred
		 (loophole :value (error "Bad argument" val pred caller))
		 caller)))

;;; is there any reason for this to be restricted and just not an
;;; alias for object->string? -- clinton
(define (stringify thing)
  (cond ((string? thing) thing)
        ((symbol? thing)
         (symbol->string thing))
        ((integer? thing)
         (number->string thing))
        (else (error "Can only stringify strings, symbols, and integers."
                     thing))))