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Re: complex arithmetic in gcc (and various standards)
"Joseph S. Myers" <joseph@codesourcery.com> writes:
| On Mon, 2 Oct 2006, Jan van Dijk wrote:
|
| > On Monday 02 October 2006 12:57, Joseph S. Myers wrote:
| > > On Mon, 2 Oct 2006, Jan van Dijk wrote:
| > > > * the C99 and C++ standards say *nothing* about the details of compex
| > > > multiplication
| > >
| > > The C99 standard says that real operands aren't converted to complex, but
| > > as I note in bug 24581, the compiler doesn't expect PLUS_EXPR and
| > > MULT_EXPR to have arguments of different types, so the front ends might
| > > need adapting to handle real * complex and real + complex specially.
| >
| > Dear Joseph,
| >
| > My question was a slightly different one. To me it is not clear whether the
| > standard allows the treatment of (r,0) as r in complex operations. For
| > example: is it allowed to handle (r,0)*(x,y) as r*(x,y)?
|
| I don't think so; at least, it might affect negative 0.
Hmm, how?
[...]
| > Triggered by 1*(Inf,0) = (Inf,NaN), I looked inside the compiler for the first
|
| (Inf,NaN) is a valid complex infinity just as (Inf,0) is; see G.3.
I think his concern is about the evaluation of 1 * (Inf, 0).
-- Gaby