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Date: Mon, 13 Aug 2012 13:16:26 -0700
From: Steve Kargl <sgk@troutmask.apl.washington.edu>
To: Stephen Montgomery-Smith <stephen@missouri.edu>
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Cc: freebsd-numerics@freebsd.org, Bruce Evans <brde@optusnet.com.au>
Subject: Re: Complex arg-trig functions
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On Mon, Aug 13, 2012 at 02:41:59PM -0500, Stephen Montgomery-Smith wrote:
> 
> Also, you made the comment that in the float version, all the 0.5 should 
> become 0.5F.  Two questions:
> 1.  Doesn't the compiler do this conversion for me?

float x, y;
y = 0.5 * x;

The conversion is effectively 'y = 0.5 * (double)x' where
now the rhs is evaluated in double (53-bit precision).  If
you have 'y = 0.5f * x', then the rhs side is evaluate
in float (24-bit precision).  For a more complicated,
expression whether one computes in 53 rather than 24 bits
can have an effect on the outcome.

-- 
Steve