Re: What is -3.I (as opposed to 0-3.I) supposed evaluate to?

["Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>]

From: "Joseph S. Myers" <joseph@codesourcery.com>

> On Mon, 8 Jun 2009, Kaveh R. GHAZI wrote:
>
> > If I write a complex double constant -3.I (as opposed to 0-3.I), what is
> > it supposed to evaluate to?  This program:
>
> Because GCC does not implement imaginary types, this applies unary minus
> to 0.0+3.0I.  Whereas 0-3.I means 0.0 - (0.0+3.0I), a mixed real/complex
> operation, the real part of whose result is 0.0 except when rounding
> towards negative infinity when it is -0.0.  There are lots of tests in
> gcc.dg/torture/complex-sign*.

Okay thanks.

Perhaps the only safe way to create the value, even in the presence of 
rounding mode changes, is to use conj(3.I) ?

       --Kaveh