[Mingw-notify] [ mingw-Bugs-925099 ] round error

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Bugs item #925099, was opened at 2004-03-29 11:15
Message generated for change (Comment added) made by dannysmith
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Category: gcc
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: RK (richardkaiser)
Assigned to: Danny Smith (dannysmith)
Summary: round error

Initial Comment:
With the C99 math.h round function 

cout<<"round: "<<round(3.64)<<endl;
cout<<"round: "<<round(3.14)<<endl;
cout<<"round: "<<round(-3.14)<<endl;
cout<<"round: "<<round(-3.64)<<endl;

I get the results 4 4 -4 -4. According to C99
(7.12.9.6) I would expect halfway cases rounded away
from zero.

Richard

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>Comment By: Danny Smith (dannysmith)
Date: 2004-03-29 20:28

Message:
Logged In: YES 
user_id=11494

Thanks for the report.  You are right, it should usually round 
to nearest, but not use the even-odd rule that 
FE_TONEAREST uses for 'halfway' values.
 
I've fixed in cvs.  round() now does this:

double
round (double x)
{
  /* Add +/- 0.5 then then round towards zero.  */
  return trunc ( x + (x >= 0.0 ?  0.5 : -0.5));
}

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