Subj : Re: Proper behavior of uneval(-0.0) ?
To   : Igor Bukanov <igor@fastmail.fm>
From : Brendan Eich <brendan@meer.net>
Date : Wed Nov 12 2003 02:22 pm

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Igor Bukanov wrote:

> while uneval(f) produces
>
> function f(i) {while (i < 10) {++i;}return 1;}


f.toSource() produces that, of course.  Try f.toSource(0) for fun.

In order to keep eval'able strings short, avoid problems with newlines 
embedded in strings passing through other layers of code, and keep 
lambdas concise when pretty-printed, I made a small (in implementation 
code size) difference from toString to toSource.  As I wrote, I'm not 
averse to a similarly small special case difference for -0, but it 
didn't seem important from a pretty-printing or newline-avoidance point 
of view, and I didn't have any use-cases motivating it.

Now that you mention it, though, I'm all for it.  See the attached 
patch, let me know what you think.

/be

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Index: jsstr.c
===================================================================
RCS file: /cvsroot/mozilla/js/src/jsstr.c,v
retrieving revision 3.82
diff -p -u -8 -r3.82 jsstr.c
--- jsstr.c	11 Nov 2003 17:59:54 -0000	3.82
+++ jsstr.c	12 Nov 2003 22:20:53 -0000
@@ -2666,16 +2666,20 @@ js_ValueToSource(JSContext *cx, jsval v)
     if (JSVAL_IS_STRING(v))
         return js_QuoteString(cx, JSVAL_TO_STRING(v), '"');
     if (!JSVAL_IS_PRIMITIVE(v)) {
         if (!js_TryMethod(cx, JSVAL_TO_OBJECT(v),
                           cx->runtime->atomState.toSourceAtom,
                           0, NULL, &v)) {
             return NULL;
         }
+    } else if (JSVAL_IS_DOUBLE(v) && JSDOUBLE_IS_NEGZERO(*JSVAL_TO_DOUBLE(v))) {
+        static const jschar js_negzero_ucstr[] = {'-', '0'};
+
+        return js_NewStringCopyN(cx, js_negzero_ucstr, 2, 0);
     }
     return js_ValueToString(cx, v);
 }
 
 JSHashNumber
 js_HashString(JSString *str)
 {
     JSHashNumber h;

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