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

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

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

> On Mon, 8 Jun 2009, Kaveh R. Ghazi wrote:
>
>> Perhaps the only safe way to create the value, even in the presence of
>> rounding mode changes, is to use conj(3.I) ?
>
> Setting the __real__ and __imag__ parts of a temporary variable should
> always be reliable for making a complex number out of arbitrary real and
> imaginary parts.

Well yes, but I meant for compile-time expressions that are exposed to fold 
even at -O0.  (Recall that I'm writing testcases for the MPC stuff.)  I'm 
not 100% confident that the temporary variable will always fold and it's too 
verbose when repeatedly used in a testcase.  With conj, the builtin will 
always fold 3.I and won't do anything unexpected with rounding modes.

I was just wondering why -3.I was evaluating differently than 0-3.I and 
whether it was a bug.  Your explanation was very useful.

        Thanks,
        --Kaveh