MATLAB Application Program Interface Reference

Determine whether or not a value is infinite

integer*4 function mexIsInf(value)
real*8 value

Arguments

value

The double-precision, floating-point number you are testing.

Returns

true if value is infinite; otherwise, returns false.

Description

Call mexIsInf to determine whether or not value is equal to infinity. MATLAB stores the value of infinity in a permanent variable named inf, which represents IEEE arithmetic positive infinity. The value of inf is built in to 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), then mexIsInf returns false. In other words, NaN is not equal to infinity.