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mxIsInf (C and Fortran)

Determine whether input is infinite

C Syntax

#include "matrix.h"
bool mxIsInf(double value);

Fortran Syntax

integer*4 mxIsInf(value)
real*8 value



Double-precision, floating-point number you are testing


Logical 1 (true) if value is infinite, and logical 0 (false) otherwise.


Call mxIsInf to determine whether value is equal to infinity or minus infinity. MATLAB® software stores the value of infinity in a permanent variable named Inf, which represents IEEE® arithmetic positive infinity. The value of the variable Inf is built into the system; you cannot modify it.

Operations that return infinity include:

  • Division by 0. For example, 5/0 returns infinity.

  • Operations resulting in overflow. For example, exp(10000) returns infinity because the result is too large to be represented on your machine.

If value equals NaN (Not-a-Number), mxIsInf returns false. In other words, NaN is not equal to infinity.


See the following examples in matlabroot/extern/examples/mx.

Introduced before R2006a

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