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std::log

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Defined in header <cmath>
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float       log( float arg );
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double      log( double arg );
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long double log( long double arg );
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double      log( Integral arg );
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Computes the natural (base e) logarithm of arg.

Contents

Parameters

arg - floating point value

Return value

natural logarithm of arg.

Domain error occurs if arg is negative. NAN is returned in that case.

Range error occurs if arg is 0. -HUGE_VAL is returned in that case.

Example

The following code computes the binary (base 2) logarithm with help of natural logarithm.

#include <cmath>
#include <iostream>
 
int main()
{
    double base = 2.0;
    double arg  = 256.0;
    double result = std::log(arg) / std::log(base);
 
    std::cout << result << '\n';
}

Output:

8

See also

Template:cpp/numeric/math/dcl list expTemplate:cpp/numeric/math/dcl list log10Template:cpp/numeric/math/dcl list powTemplate:cpp/numeric/complex/dcl list logTemplate:cpp/numeric/valarray/dcl list log