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ln(+Number, ?Result)
Evaluates the natural logarithm ln(Number) and unifies the resulting value
with Result.
- +Number
- A number.
- ?Result
- A variable 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 a free variable, the call to ln/2 is
delayed until this variable is instantiated.
Fail Conditions
Fails if the result of the evaluation does not unify with Result.
Resatisfiable
Exceptions
- (4) instantiation fault
- Number is not instantiated (non-coroutining mode only).
- (5) type error
- Result is a number but not a float or breal.
- (24) number expected
- Number is not of a numeric type.
- (24) number expected
- Result is neither a number nor a variable.
- (20) arithmetic exception
- Illegal arithmetic operation: Number is 0 or less.
Examples
Success:
ln(2.0, Result). (gives Result = 0.693147)
ln(1, Result). (gives Result = 0.0)
Fail:
ln(1, 1.0).
Error:
ln(A, 6.0). (Error 4).
ln(1, 0). (Error 5).
ln(-2, Result). (Error 20).
ln(0, Result). (Error 20).
ln(4 + 2, 1.79176). (Error 24).
ln(1, r). (Error 24).
See Also
is / 2