std::numeric_limits<double>::epsilon() undefined in Visual C++ 2015

Question

The following code produces an error: std::numeric_limits<double>::epsilon() undefined error.

Using numeric_limits<double>::epsilon also produces this error.

#ifndef _USE_MATH_DEFINES
#define _USE_MATH_DEFINES
#endif // !_USE_MATH_DEFINES

#include <math.h>
#include <limits.h>

class plusCartesianPoly {

public:

    static bool isClose(double a, double b)
    {
        if (fabs(a-b) <= std::numeric_limits::epsilon())
            return true;

        return(false);
    }
};

std::numeric_limits is defined in <limits>, not <limits.h>. — Pete Becker
– Pete Becker, Commented Aug 19, 2016 at 13:29
General rule of thumb: never user *.h includes for things from std. — Torbjörn
– Torbjörn, Commented Aug 19, 2016 at 13:30
OT, It could be a better idea to scale epsilon somehow. See the example code in the reference page. — Bob__
– Bob__, Commented Aug 19, 2016 at 15:49

rocambille · Accepted Answer · 2016-08-19 13:40:43Z

5

numeric_limits is declared in limits, not limits.h which is the C version of climits (by the way, math.h is the C version of cmath):

#ifndef _USE_MATH_DEFINES
#define _USE_MATH_DEFINES
#endif // !_USE_MATH_DEFINES

#include <cmath>
#include <limits>

class plusCartesianPoly {

public:

    static bool isClose(double a, double b)
    {
        if (std::fabs(a-b) <= std::numeric_limits<double>::epsilon())
            return true;

        return(false);
    }
};

edited Aug 19, 2016 at 13:40

answered Aug 19, 2016 at 13:32

rocambille

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Bathsheba · Accepted Answer · 2016-08-19 13:32:06Z

4

<limits.h> contains the macro-type limits from the C standard library

You need <limits> to use the C++ standard library functions.

answered Aug 19, 2016 at 13:32

Bathsheba

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