Since Alex isn't on python-dev, forwarding this for his convenience (he said he wanted to reply.) Tim also replied to his checkin, but I didn't forward that message.
---------- Forwarded message ----------
From: Thomas Wouters <[EMAIL PROTECTED]>
Date: Aug 24, 2006 12:16 AM
Subject: Re: [Python-checkins] r51525 - in python/trunk: Lib/test/test_float.py Objects/floatobject.c
To: "alex. martelli" <[EMAIL PROTECTED]>
On 8/23/06,
alex.martelli <[EMAIL PROTECTED]> wrote:
--- python/trunk/Objects/floatobject.c (original)
+++ python/trunk/Objects/floatobject.c Wed Aug 23 22:42:02 2006
@@ -821,12 +821,12 @@
ix = pow(iv, iw);
PyFPE_END_PROTECT(ix)
Py_ADJUST_ERANGE1(ix);
- if (errno != 0) {
+ /* we need to ignore ERANGE here and just return inf */
+ if (errno != 0 && errno != ERANGE) {
/* We don't expect any errno value other than ERANGE, but
* the range of libm bugs appears unbounded.
*/
- PyErr_SetFromErrno(errno == ERANGE ? PyExc_OverflowError :
- PyExc_ValueError);
+ PyErr_SetFromErrno(PyExc_ValueError);
return NULL;
I don't think this can be right. The returnvalue of pow() in the case of ERANGE isn't defined anywhere that I can find, at least. How can we assume it is +Infinity? As I tried to say over the visiphone, you can't even use compile-time or startup-time checks for the behaviour because 'undefined' also means it need not be consistent, either. The best we could do, if we really wanted to return +inf instead of raising OverflowError (which I don't, but don't really care about either), is generate +Infinity in some guaranteed way. I'm sure Tim can come up with a convenient, portable way < 0.9 wink>.
But I'd prefer to keep it the way it was: x*x and x**2 don't always do the same thing. Floats have a lot more confusing features like that, such as 10*x - 9*x need not be x. I don't see the added value of trying to make it consistent in just this case, even if it's portable.
--
Thomas Wouters <[EMAIL PROTECTED]>
Hi! I'm a .signature virus! copy me into your .signature file to help me spread!
--
Thomas Wouters <[EMAIL PROTECTED]>
Hi! I'm a .signature virus! copy me into your .signature file to help me spread!
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