The GNU C Library - Exponents and Logarithms

Exponentiation and Logarithms

Function double exp (double x)

The exp function returns the value of e (the base of natural logarithms) raised to power x.

The function fails, and sets errno to ERANGE , if the magnitude of the result is too large to be representable.

Function double log (double x)

This function returns the natural logarithm of x. exp (log (x)) equals x, exactly in mathematics and approximately in C.

The following errno error conditions are defined for this function:

EDOM

The argument x is negative. The log function is defined mathematically to return a real result only on positive arguments.

ERANGE

The argument is zero. The log of zero is not defined.

Function double log10 (double x)

This function returns the base-10 logarithm of x. Except for the different base, it is similar to the log function. In fact, log10 (x) equals log (x) / log (10) .

Function double pow (double base, double power)

This is a general exponentiation function, returning base raised to power.

The following errno error conditions are defined for this function:

EDOM

The argument base is negative and power is not an integral value. Mathematically, the result would be a complex number in this case.

ERANGE

An underflow or overflow condition was detected in the result.

Function double sqrt (double x)

This function returns the nonnegative square root of x.

The sqrt function fails, and sets errno to EDOM , if x is negative. Mathematically, the square root would be a complex number.

Function double cbrt (double x)

This function returns the cube root of x. This function cannot fail; every representable real value has a representable real cube root.

Function double hypot (double x, double y)

The hypot function returns sqrt (x*x + y*y) . (This is the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin.) See also the function cabs in Absolute Value.

Function double expm1 (double x)

This function returns a value equivalent to exp (x) - 1 . It is computed in a way that is accurate even if the value of x is near zero---a case where exp (x) - 1 would be inaccurate due to subtraction of two numbers that are nearly equal.

Function double log1p (double x)

This function returns a value equivalent to log (1 + x) . It is computed in a way that is accurate even if the value of x is near zero.