isfinite

From cppreference.com
< c‎ | numeric‎ | math
Common mathematical functions
Functions
Basic operations
(C99)
(C99)
(C99)
(C99)
(C99) (C99) (C99) (C23)
Maximum/minimum operations
(C99)
(C99)
(C23)
(C23)
(C23)
Exponential functions
(C23)
(C99)
(C99)
(C23)
(C23)

(C99)
(C99)(C23)
(C23)
(C23)
Power functions
(C99)
(C23)
(C23)

(C99)
(C23)
(C23)
(C23)
Trigonometric and hyperbolic functions
(C23)
(C23)
(C23)
(C23)
(C99)
(C99)
(C99)
Nearest integer floating-point
(C99)(C99)(C99)
(C23)
(C99)

(C99)
(C99)(C99)(C99)
(C23) (C23) (C23) (C23)
Floating-point manipulation
(C99)(C99)
(C99)(C23)
(C99)
(C99)(C99)
(C23)(C23)
(C99)
(C23)
Narrowing operations
(C23)
(C23)
(C23)
(C23)
(C23)
(C23)
Quantum and quantum exponent
(C23)
(C23)
Decimal re-encoding functions
(C23)
(C23)
(C23)
(C23)
Total order and payload functions
(C23)
(C23)
Classification
(C99)
(C23)
isfinite
(C99)
(C99)
(C99)
(C99)
(C99)
(C23)
(C23)
(C99)
(C99)
(C99)
(C99)
(C23)
(C23)

Error and gamma functions
(C99)
(C99)
(C99)
(C99)
Types
Macro constants
Special floating-point values
(C99)(C23)
Arguments and return values
(C99) (C99) (C99) (C99) (C99)
Error handling
Fast operation indicators
Defined in header <math.h>
#define isfinite(arg) /* implementation defined */
(since C99)

Determines if the given floating-point number arg has finite value i.e. it is normal, subnormal or zero, but not infinite or NaN. The macro returns an integral value.

FLT_EVAL_METHOD

Parameters

arg - floating-point value

Return value

Nonzero integral value if arg has finite value, 0 otherwise.

Example

#include <float.h>
#include <math.h>
#include <stdio.h>
 
int main(void)
{
    printf("isfinite(NAN)         = %d\n", isfinite(NAN));
    printf("isfinite(INFINITY)    = %d\n", isfinite(INFINITY));
    printf("isfinite(0.0)         = %d\n", isfinite(0.0));
    printf("isfinite(DBL_MIN/2.0) = %d\n", isfinite(DBL_MIN / 2.0));
    printf("isfinite(1.0)         = %d\n", isfinite(1.0));
    printf("isfinite(exp(800))    = %d\n", isfinite(exp(800)));
}

Possible output:

isfinite(NAN)         = 0
isfinite(INFINITY)    = 0
isfinite(0.0)         = 1
isfinite(DBL_MIN/2.0) = 1
isfinite(1.0)         = 1
isfinite(exp(800))    = 0

References

  • C23 standard (ISO/IEC 9899:2024):
  • 7.12.3.2 The isfinite macro (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
  • 7.12.3.2 The isfinite macro (p: TBD)
  • C11 standard (ISO/IEC 9899:2011):
  • 7.12.3.2 The isfinite macro (p: 236)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.12.3.2 The isfinite macro (p: 216-217)

See also

(C99)
classifies the given floating-point value
(function macro)
(C99)
checks if the given number is infinite
(function macro)
(C99)
checks if the given number is NaN
(function macro)
(C99)
checks if the given number is normal
(function macro)
C++ documentation for isfinite