Allow for approx comparison of floats in tests

defexample entries may now include a symbol `~>' instead of `=>' which
uses an approximate comparison instead of `equal' to compare actual and
expected floating-point values.

Also, for completeness, add support for the `should-error' symbol `!!>' in
`examples-to-docs.el'. This is formatted as the comment ";; Error"

dev/examples-to-docs.el

@@ -5,9 +5,15 @@
 (defvar functions '())
 
 (defun example-to-string (example)
-  (let ((actual (car example))
+  (-let* (((actual sym expected) example)
-        (expected (nth 2 example)))
+	  (comment
-    (--> (format "%S ;; => %S" actual expected)
+	   (cond
+	    ((eq sym '=>) (format "=> %S" expected))
+	    ((eq sym '~>) (format "~> %S" expected))
+	    ((eq sym '!!>) (format "Error"))
+	    (t (error "Invalid test case: %S" `(,actual ,sym ,expected))))))
+    (--> comment
+      (format "%S ;; %s" actual it)
       (replace-regexp-in-string "\\\\\\?" "?" it)
       (replace-regexp-in-string "\n" "\\n" it t t)
       (replace-regexp-in-string "\t" "\\t" it t t)

dev/examples-to-tests.el

@@ -3,6 +3,8 @@
 (defun example-to-should (actual sym expected)
   (cond ((eq sym '=>)
          `(should (equal ,actual ,expected)))
+	((eq sym '~>)
+	 `(should (approx-equal ,actual ,expected)))
         ((eq sym '!!>)
          `(should-error (eval ',actual) :type ',expected))
         (t

dev/examples.el

@@ -9,6 +9,17 @@
 (defun square (num) (* num num))
 (defun three-letters () '("A" "B" "C"))
 
+;; Allow approximate comparison of floating-point results, to work
+;; around differences in implementation between systems. Use the `~>'
+;; symbol instead of `=>' to test the expected and actual values with
+;; `approx-equal'
+(defvar epsilon 1e-15)
+(defun approx-equal (u v)
+  (or (= u v)
+      (< (/ (abs (- u v))
+	    (max (abs u) (abs v)))
+	 epsilon)))
+
 (def-example-group "Maps"
   "Functions in this category take a transforming function, which
 is then applied sequentially to each or selected elements of the
@@ -977,5 +988,5 @@ new list."
                     (funcall (-prodfn (-compose f ff) (-compose g gg)) input3)))) => t)))
 
 ;; Local Variables:
-;; eval: (font-lock-add-keywords nil '(("defexamples\\|def-example-group\\| => \\| !!> " (0 'font-lock-keyword-face)) ("(defexamples[[:blank:]]+\\(.*\\)" (1 'font-lock-function-name-face))))
+;; eval: (font-lock-add-keywords nil '(("defexamples\\|def-example-group\\| => \\| !!> \\| ~>" (0 'font-lock-keyword-face)) ("(defexamples[[:blank:]]+\\(.*\\)" (1 'font-lock-function-name-face))))
 ;; End: