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ln(+Number, -Result)

-Result is ln(+Number)

Evaluates the natural logarithm ln(Number) and unifies the resulting value with Result.
Number
A number.
Result
Output: float or breal.

Description

Evaluates the natural logarithm ln(Number) and unifies the resulting value with Result.

This predicate can be used as a function in arithmetic expressions. In coroutining mode, if Number is uninstantiated, the call to ln/2 is delayed until this variable is instantiated.

Modes and Determinism

Exceptions

(4) instantiation fault
Number is not instantiated (non-coroutining mode only).
(24) number expected
Number is not of a numeric type.
(20) arithmetic exception
Illegal arithmetic operation: Number is 0 or less.

Examples

Success:
    Result is ln(2.0).          % gives Result = 0.693147
    Result is ln(1).            % gives Result = 0.0

Error:
    Result is ln(-2).           % arithmetic exception
    Result is ln(0).            % arithmetic exception

See Also

is / 2