Merge pull request #120 from verdammelt/binary-update

Adding more test cases to improve binary exercise.

exercises/binary/binary-test.lisp

@@ -31,6 +31,18 @@
 (define-test invalid-binary-is-decimal-0
   (assert-equal 0 (binary:to-decimal "carrot")))
 
+(define-test invalid-characters-at-beginning
+  (assert-equal 2 (binary:to-decimal "a10")))
+
+(define-test invalid-characters-at-end
+  (assert-equal 2 (binary:to-decimal "10a")))
+
+(define-test invalid-characters-in-middle
+  (assert-equal 2 (binary:to-decimal "1a0")))
+
+(define-test invalid-digits
+  (assert-equal 0 (binary:to-decimal "23")))
+
 #-xlisp-test
 (let ((*print-errors* t)
       (*print-failures* t))

exercises/binary/example.lisp

@@ -4,33 +4,7 @@
 
 (in-package #:binary)
 
-;; (defun to-decimal (string)
-;;   (or (parse-integer string :radix 2 :junk-allowed t)
-;;       0))
-
-;; (defun to-decimal (string)
-;;   (flet ((parse-digit (digit) (if (and digit (char= digit #\1)) 1 0)))
-;;     (do* ((digits (reverse (coerce string 'list)) (rest digits))
-;;           (digit (parse-digit (car digits))
-;;                  (parse-digit (car digits)))
-;;           (index 0 (incf index))
-;;           (value (* digit
-;;                     (expt 2 index))
-;;                  (+ value (* digit
-;;                              (expt 2 index)))))
-;;          ((null digits) value))))
-
-;; (defun to-decimal (string)
-;;   (flet ((parse-digit (digit) (or (digit-char-p digit 2) 0)))
-;;     (do* ((index 0 (incf index))
-;;           (revstr (reverse string))
-;;           (digit (parse-digit (char revstr index))
-;;                  (parse-digit (char revstr index)))
-;;           (value digit (+ value (* digit (expt 2 index)))))
-;;          ((= (1+ index) (length string)) value))))
-
 (defun to-decimal (string)
-  (loop with revstr = (reverse string)
-     for idx below (length string) and c across revstr
-     for digit = (or (digit-char-p c 2) 0)
-     summing (* digit (expt 2 idx))))
+  (loop with digits = (remove-if #'null (map 'list #'(lambda (c) (digit-char-p c 2)) string))
+     for idx below (length digits) and digit in (reverse digits)
+       summing (* digit (expt 2 idx))))