Better parse-integer

diff --git a/ecmalisp.lisp b/ecmalisp.lisp
index cb89dfc..80e2b77 100644 (file)
--- a/ecmalisp.lisp
+++ b/ecmalisp.lisp
@@ -438,13 +438,32 @@
        (error "Unsupported argument."))))
 
   (defun parse-integer (string)
-    (let ((value 0)
-          (index 0)
-          (size (length string)))
-      (while (< index size)
-        (setq value (+ (* value 10) (digit-char-p (char string index))))
-        (incf index))
-      value))
+    (block nil
+      (let ((value 0)
+           (index 0)
+           (size (length string))
+           (sign 1))
+       (when (zerop size) (return (values nil 0)))
+       ;; Optional sign
+       (case (char string 0)
+         (#\+ (incf index))
+         (#\- (setq sign -1)
+              (incf index)))
+       ;; First digit
+       (unless (and (< index size)
+                    (setq value (digit-char-p (char string index))))
+         (values nil index))
+       (incf index)
+       ;; Other digits
+       (while (< index size)
+         (let ((digit (digit-char-p (char string index))))
+           (unless digit (return))
+           (setq value (+ (* value 10) digit))
+           (incf index)))
+       (if (or (= index size)
+               (char= (char string index) #\space))
+           (values (* sign value) index)
+           (values nil index)))))
 
   (defun some (function seq)
     (cond