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Diffstat (limited to 'src/math/s_logb.c')
-rw-r--r-- | src/math/s_logb.c | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/src/math/s_logb.c b/src/math/s_logb.c new file mode 100644 index 0000000..be399c7 --- /dev/null +++ b/src/math/s_logb.c @@ -0,0 +1,34 @@ +/* @(#)s_logb.c 5.1 93/09/24 */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunPro, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* + * double logb(x) + * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. + * Use ilogb instead. + */ + +#include <math.h> +#include "math_private.h" + +double +logb(double x) +{ + int32_t lx,ix; + EXTRACT_WORDS(ix,lx,x); + ix &= 0x7fffffff; /* high |x| */ + if((ix|lx)==0) return -1.0/fabs(x); + if(ix>=0x7ff00000) return x*x; + if((ix>>=20)==0) /* IEEE 754 logb */ + return -1022.0; + else + return (double) (ix-1023); +} |