diff options
Diffstat (limited to 'newlib/libm/common/s_isnan.c')
| -rw-r--r-- | newlib/libm/common/s_isnan.c | 113 |
1 files changed, 92 insertions, 21 deletions
diff --git a/newlib/libm/common/s_isnan.c b/newlib/libm/common/s_isnan.c index b0c40369a..5ae6c9b81 100644 --- a/newlib/libm/common/s_isnan.c +++ b/newlib/libm/common/s_isnan.c @@ -13,8 +13,21 @@ /* FUNCTION - <<isnan>>, <<isnanf>>, <<isinf>>, <<isinff>>, <<finite>>, <<finitef>>---test for exceptional numbers +<<fpclassify>>, <<isfinite>>, <<isinf>>, <<isnan>>, and <<isnormal>>--floating-point classification macros; <<finite>>, <<finitef>>, <<isinf>>, <<isinff>>, <<isnan>>, <<isnanf>>--test for exceptional numbers +@c C99 (start +INDEX + fpclassify +INDEX + isfinite +INDEX + isinf +INDEX + isnan +INDEX + isnormal +@c C99 end) +@c SUSv2 (start INDEX isnan INDEX @@ -28,8 +41,18 @@ INDEX isinff INDEX finitef +@c SUSv2 end) ANSI_SYNOPSIS + [C99 standard macros:] + #include <math.h> + int fpclassify(real-floating <[x]>); + int isfinite(real-floating <[x]>); + int isinf(real-floating <[x]>); + int isnan(real-floating <[x]>); + int isnormal(real-floating <[x]>); + + [Archaic SUSv2 functions:] #include <ieeefp.h> int isnan(double <[arg]>); int isinf(double <[arg]>); @@ -38,30 +61,64 @@ ANSI_SYNOPSIS int isinff(float <[arg]>); int finitef(float <[arg]>); -TRAD_SYNOPSIS - #include <ieeefp.h> - int isnan(<[arg]>) - double <[arg]>; - int isinf(<[arg]>) - double <[arg]>; - int finite(<[arg]>); - double <[arg]>; - int isnanf(<[arg]>); - float <[arg]>; - int isinff(<[arg]>); - float <[arg]>; - int finitef(<[arg]>); - float <[arg]>; - - DESCRIPTION - These functions provide information on the floating-point +<<fpclassify>>, <<isfinite>>, <<isinf>>, <<isnan>>, and <<isnormal>> are macros +defined for use in classifying floating-point numbers. This is a help because +of special "values" like NaN and infinities. In the synopses shown, +"real-floating" indicates that the argument is an expression of real floating +type. These function-like macros are C99 and POSIX-compliant, and should be +used instead of the now-archaic SUSv2 functions. + +The <<fpclassify>> macro classifies its argument value as NaN, infinite, normal, +subnormal, zero, or into another implementation-defined category. First, an +argument represented in a format wider than its semantic type is converted to +its semantic type. Then classification is based on the type of the argument. +The <<fpclassify>> macro returns the value of the number classification macro +appropriate to the value of its argument: + +o+ +o FP_INFINITE + <[x]> is either plus or minus infinity; +o FP_NAN + <[x]> is "Not A Number" (plus or minus); +o FP_NORMAL + <[x]> is a "normal" number (i.e. is none of the other special forms); +o FP_SUBNORMAL + <[x]> is too small be stored as a regular normalized number (i.e. loss of precision is likely); or +o FP_ZERO + <[x]> is 0 (either plus or minus). +o- + +The "<<is>>" set of macros provide a useful set of shorthand ways for +classifying floating-point numbers, providing the following equivalent +relations: + +o+ +o <<isfinite>>(<[x]>) +returns non-zero if <[x]> is finite. (It is equivalent to +(<<fpclassify>>(<[x]>) != FP_INFINITE && <<fpclassify>>(<[x]>) != FP_NAN).) + +o <<isinf>>(<[x]>) +returns non-zero if <[x]> is infinite. (It is equivalent to +(<<fpclassify>>(<[x]>) == FP_INFINITE).) + +o <<isnan>>(<[x]>) +returns non-zero if <[x]> is NaN. (It is equivalent to +(<<fpclassify>>(<[x]>) == FP_NAN).) + +o <<isnormal>>(<[x]>) +returns non-zero if <[x]> is normal. (It is equivalent to +(<<fpclassify>>(<[x]>) == FP_NORMAL).) +o- + + The archaic SUSv2 functions provide information on the floating-point argument supplied. - There are five major number formats: + There are five major number formats ("exponent" referring to the + biased exponent in the binary-encoded number): o+ o zero - A number which contains all zero bits. + A number which contains all zero bits, excluding the sign bit. o subnormal A number with a zero exponent but a nonzero fraction. o normal @@ -85,7 +142,21 @@ DESCRIPTION and <<isinf>> are macros that operate on multiple types of floating-point. The SUSv2 standard declares <<isnan>> as a function taking double. Newlib has decided to declare - them both as macros in math.h and as functions in ieeefp.h. + them both as macros in math.h and as functions in ieeefp.h to + maintain backward compatibility. + +RETURNS +@comment Formatting note: "$@" forces a new line +The fpclassify macro returns the value corresponding to the appropriate FP_ macro.@* +The isfinite macro returns nonzero if <[x]> is finite, else 0.@* +The isinf macro returns nonzero if <[x]> is infinite, else 0.@* +The isnan macro returns nonzero if <[x]> is an NaN, else 0.@* +The isnormal macro returns nonzero if <[x]> has a normal value, else 0. + +PORTABILITY +math.h macros are C99, POSIX. + +ieeefp.h funtions are outdated and should be avoided. QUICKREF isnan - pure |