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ln(+Number, -Result)

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

Description

This predicate is used by the ECLiPSe compiler to expand evaluable arithmetic expressions. So the call to ln(Number, Result) is equivalent to 
    Result is ln(Number)
which should be preferred for portability.

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