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msvcrt: Don't depend on the system's implementation of acos() & asin().

This commit is contained in:
Henri Verbeet 2008-08-29 02:11:53 +02:00 committed by Alexandre Julliard
parent 5c1edcfaad
commit 71aa14af99
1 changed files with 7 additions and 2 deletions
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9
dlls/msvcrt/math.c
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@ -57,7 +57,12 @@ static MSVCRT_matherr_func MSVCRT_default_matherr_func = NULL;
double CDECL MSVCRT_acos( double x )
{
if (x < -1.0 || x > 1.0 || !finite(x)) *MSVCRT__errno() = MSVCRT_EDOM;
return acos(x);
/* glibc implements acos() as the FPU equivalent of atan2(sqrt(1 - x ^ 2), x).
* asin() uses a similar construction. This is bad because as x gets nearer to
* 1 the error in the expression "1 - x^2" can get relatively large due to
* cancellation. The sqrt() makes things worse. A safer way to calculate
* acos() is to use atan2(sqrt((1 - x) * (1 + x)), x). */
return atan2(sqrt((1 - x) * (1 + x)), x);
}
/*********************************************************************
@ -66,7 +71,7 @@ double CDECL MSVCRT_acos( double x )
double CDECL MSVCRT_asin( double x )
{
if (x < -1.0 || x > 1.0 || !finite(x)) *MSVCRT__errno() = MSVCRT_EDOM;
return asin(x);
return atan2(x, sqrt((1 - x) * (1 + x)));
}
/*********************************************************************