Better looks_like_number() function [sv.c]

The old looks_like_number() function was too forgiving.  It classified
strings like these as numbers:

   "+"
   "+e+"
   "e3"
   "."

With this patch perl -lwe 'print int(".")' prints:

   Argument "." isn't numeric in int at -e line 1.
   0

as it should and perl still passes all its tests.

p5p-msgid: <199702141708.SAA17546@bergen.sn.no>

diff --git a/sv.c b/sv.c
index 528afd9..2ea1990 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -1504,7 +1504,7 @@ SV *sv;
     register char *s;
     register char *send;
     register char *sbegin;
-    I32 numtype = 1;
+    I32 numtype;
     STRLEN len;
 
     if (SvPOK(sv)) {
@@ -1520,31 +1520,53 @@ SV *sv;
     s = sbegin;
     while (isSPACE(*s))
        s++;
-    if (s >= send)
-       return 0;
     if (*s == '+' || *s == '-')
        s++;
-    while (isDIGIT(*s))
-       s++;
-    if (s == send)
-       return numtype;
-    if (*s == '.') {
-       numtype = 1;
-       s++;
+
+    /* next must be digit or '.' */
+    if (isDIGIT(*s)) {
+        do {
+           s++;
+        } while (isDIGIT(*s));
+        if (*s == '.') {
+           s++;
+            while (isDIGIT(*s))  /* optional digits after "." */
+                s++;
+        }
     }
-    else if (s == SvPVX(sv))
-       return 0;
-    while (isDIGIT(*s))
-       s++;
-    if (s == send)
-       return numtype;
+    else if (*s == '.') {
+        s++;
+        /* no digits before '.' means we need digits after it */
+        if (isDIGIT(*s)) {
+           do {
+               s++;
+            } while (isDIGIT(*s));
+        }
+        else
+           return 0;
+    }
+    else
+        return 0;
+
+    /*
+     * we return 1 if the number can be converted to _integer_ with atol()
+     * and 2 if you need (int)atof().
+     */
+    numtype = 1;
+
+    /* we can have an optional exponent part */
     if (*s == 'e' || *s == 'E') {
        numtype = 2;
        s++;
        if (*s == '+' || *s == '-')
            s++;
-       while (isDIGIT(*s))
-           s++;
+        if (isDIGIT(*s)) {
+            do {
+                s++;
+            } while (isDIGIT(*s));
+        }
+        else
+            return 0;
     }
     while (isSPACE(*s))
        s++;