Defined in header <math.h>
#define islessgreater(x, y) /* implementation defined */
(since C99)

Determines if the floating point number x is less than or greater than the floating-point number y, without setting floating-point exceptions.


x - floating point value
y - floating point value

Return value

Nonzero integral value if x < y || x > y, ​0​ otherwise.


The built-in operator< and operator> for floating-point numbers may raise FE_INVALID if one or both of the arguments is NaN. This function is a "quiet" version of the expression x < y || x > y. The macro does not evaluate x and y twice.


#include <stdio.h>
#include <math.h>
int main(void)
    printf("islessgreater(2.0,1.0)      = %d\n", islessgreater(2.0,1.0));
    printf("islessgreater(1.0,2.0)      = %d\n", islessgreater(1.0,2.0));
    printf("islessgreater(1.0,1.0)      = %d\n", islessgreater(1.0,1.0));
    printf("islessgreater(INFINITY,1.0) = %d\n", islessgreater(INFINITY,1.0));
    printf("islessgreater(1.0,NAN)      = %d\n", islessgreater(1.0,NAN));
    return 0;

Possible output:

islessgreater(2.0,1.0)      = 1
islessgreater(1.0,2.0)      = 1
islessgreater(1.0,1.0)      = 0
islessgreater(INFINITY,1.0) = 1
islessgreater(1.0,NAN)      = 0


  • C11 standard (ISO/IEC 9899:2011):
    • The islessgreater macro (p: 261)
    • F.10.11 Comparison macros (p: 531)
  • C99 standard (ISO/IEC 9899:1999):
    • The islessgreater macro (p: 241-242)

See also

checks if the first floating-point argument is less than the second
(function macro)
checks if the first floating-point argument is greater than the second
(function macro)
C++ documentation for islessgreater

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