A binary function which returns the result of computing the logarithm of a specified number to a specified base. (Logarithm Fn NUMBER BASE) returns log_BASE(NUMBER), i.e. the logarithm of NUMBER in base BASE, where NUMBER is an instance of positive number and BASE is an instance of non-negative number. It returns instances of real number.

Note that (Exponent Fn BASE (Logarithm Fn NUMBER BASE)) = NUMBER.

See also Log Fn, a unary function which returns the logarithm of a number in base e.