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;; Error checking helpers
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;; The following procedures may be used to help out writing 
;; defensive code by allowing you to immediately signal an
;; error when a problem is detected.
;;
;; The following example shows several different ways of
;; using the assertion procedures.
;;    (define (my-add x y)
;;      (assert-t (number? x))
;;      (assert y number?)
;;      (+ x y))

;; Generates an error message if applying the pred procedure
;; to test-val does not generate a true value.
(define (assert test-val pred)
  (if (not (pred test-val))
      (error "ASSERT FAILED: " test-val pred)))

;; Generates an error if test-val and expected-val are not
;; equal?
(define (assert-equal test-val expected-val)
  (if (not (equal? test-val expected-val))
      (error "ASSERT-EQUAL FAILED: \n" 
             "  Expected value: " expected-val "\n"
             "  Actual value: " test-val "\n")))

;; Generates an error if test-val and expected-val are not
;; eqv?
(define (assert-eqv test-val expected-val)
  (if (not (eqv? test-val expected-val))
      (error "ASSERT-EQV FAILED: \n" 
             "  Expected value: " expected-val "\n"
             "  Actual value: " test-val "\n")))

;; Generates an error if test-val and expected-val are not
;; eq?
(define (assert-eq test-val expected-val)
  (if (not (eq? test-val expected-val))
      (error "ASSERT-EQ FAILED: \n" 
             "  Expected value: " expected-val "\n"
             "  Actual value: " test-val "\n")))

;; Generates an error if test-val and expected-val are not
;; =
(define (assert= test-val expected-val)
  (if (not (= test-val expected-val))
      (error "ASSERT= FAILED: \n" 
             "  Expected value: " expected-val "\n"
             "  Actual value: " test-val "\n")))

;; Generates an error if test-val is not #f
(define (assert-f test-val)
  (if test-val
      (error "ASSERT-F FAILED")))

;; Generates an error if test-value is #f
(define (assert-t test-val)
  (if (not test-val)
      (error "ASSERT-T FAILED")))

Last updated: 2008-01-25 09:23:57 -0500