fpclassify(3M)

fpclassify, isfinite, isinf, isnan, isnormal, signbit, isless, islessequal, islessgreater, isgreater, isgreaterequal, isunordered -- floating point classification macros

Synopsis

   cc [flag ...] file ...  -lm [library ...]
   
   #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);
   

   int signbit(real-floating x);
   

   int isless(real-floating x, real-floating y);
   

   int islessequal(real-floating x, real-floating y);
   

   int islessgreater(real-floating x, real-floating y);
   

   int isgreater(real-floating x, real-floating y);
   

   int isgreaterequal(real-floating x, real-floating y);
   

   int isunordered(real-floating x, real-floating y);

Description

The fpclassify macro classifies x 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.

NOTE: Since an expression can be evaluated with more range and precision than its type has, it is important to know the type that classification is based on. For example, a normal long double value might become subnormal when converted to double, and zero when converted to float.

The fpclassify macro returns the value of the number classification macro appropriate to x.

The isfinite macro determines whether x has a finite value (zero, subnormal, or normal, and not infinite or NaN). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.

The isfinite macro returns a nonzero value only if x has a finite value.

The isinf macro determines whether x is an infinity (positive or negative). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.

The isinf macro returns a nonzero value only if x has infinite value.

The isnan macro determines whether x is a NaN. First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.

NOTE: For the isnan macro, the type for determination does not matter unless the implementation supports NaNs in the evaluation type but not in the semantic type.

The isnan macro returns a nonzero value only if x has a NaN value.

The isnormal macro determines whether x is normal (neither zero, subnormal, infinite, nor NaN). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.

The isnormal macro returns a nonzero value only if x has a normal value.

The signbit macro determines whether the sign of x is negative.

NOTE: The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is unsigned, it is treated as positive.

The signbit macro returns a nonzero value if the sign of x is negative.

The isless macro determines whether x is less than y. The value of isless(x, y) is always equal to (x) < (y); however, unlike (x) < (y), isless(x, y) does not raise the invalid floating-point exception when x and y are unordered.

The isless macro returns the value of (x) < (y).

The islessequal macro determines whether x is less than or equal to y. The value of islessequal(x, y) is always equal to (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise the invalid floating-point exception when x and y are unordered.

The islessequal macro returns the value of (x) <= (y).

The islessgreater macro determines whether x is less than or greater than x. The islessgreater(x, y) macro is similar to (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise the invalid floating-point exception when x and y are unordered (nor does it evaluate x and y twice).

The islessgreater macro returns the value of (x) < (y) || (x) > (y).

The isgreater macro determines whether x is greater than y. The value of isgreater(x, y) is always equal to (x) > (y); however, unlike (x) > (y), isgreater(x, y) does not raise the invalid floating-point exception when x and y are unordered.

The isgreater macro returns the value of (x) > (y).

The isgreaterequal macro determines whether x is greater than or equal to y. The value of isgreaterequal(x, y) is always equal to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does not raise the invalid floating-point exception when x and y are unordered.

The isgreaterequal macro returns the value of (x) >= (y).

The isunordered macro determines whether x and y are unordered.

The isunordered macro returns 1 if x and y are unordered and 0 otherwise.

References

cc(1)