__builtin_cpow((0,0),(0,0))

[Gabriel Dos Reis]

Ronny Peine <RonnyPeine@gmx.de> writes:

| Dave Korn wrote:
| > ----Original Message----
| >
| >>From: Ronny Peine
| >>Sent: 16 March 2005 17:34
| >
| >>See for example:
| >>http://mathworld.wolfram.com/ExponentLaws.html
| >>
| >   Ok, I did.
| >
| >> Even though, gcc returns 1 for pow(0.0,0.0) in version 3.4.3 like
| >> many other c-compiler do. The same behaviour would be expected from
| >> cpow.
| >   No, you're wrong (that the same behaviour would be expected from
| > cpow).
| > See for example:
| > http://mathworld.wolfram.com/ExponentLaws.html
| > " Note that these rules apply in general only to real quantities,
| > and can
| > give manifestly wrong results if they are blindly applied to complex
| > quantities. "
| > <g>
| 
| Well yes in the general case it's not applieable, but x^0 is 1 in the
| complex case, too.

Just repeating it does not make it a reality.

| And if 0^0 is converted from the real to the
| complex domain (it's even a part of the complex domain) than the same
| behaviour would be expected, otherwise the definition wouldn't be very
| well.

the point is that real or exponentiation is not the same as integer
exponentiation.  The latter has less freedom that ther former.

| Has anyone found a hint in the ieee754 standard if there is something
| about it in there? I haven't one here right now, well it's not
| prizeless. Otherwise these discussion won't end.

there are several standards, among which IEEE-754 and the ISO standard
LIA (designed to correct the IEEE-754 shot).  IEEE-754 does not
concern itself with complex arithmetic (though C99 made some
interesting and innovative extensions).  I already quoted part 2 of
LIA. Part 3 of LIA, concerning complex arithmetic, is being developed
and is in its second stage.  It is consistent with LIA-2.

-- Gaby