[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]
-(+Number, ?Result)
Unifies the negative of Number with Result.
- +Number
- A number.
- ?Result
- A variable or a number.
Description
This predicate is used by the ECLiPSe compiler to expand evaluable
arithmetic expressions. So the call to -(Number, Result) is equivalent
to
Result is -Number
which should be preferred for portability.
Number and Result have to be of the same type.
In coroutining mode, if Number is a free variable, the call to -/2 is
delayed until this variable is instantiated.
Fail Conditions
Fails if the result of the evaluation does not unify with Result.
Resatisfiable
No
Exceptions
- (4) instantiation fault
- Number is not instantiated (non-coroutining mode only).
- (5) type error
- Result and Number are numbers of different types.
- (24) number expected
- Number is not of a numeric type.
- (24) number expected
- Result is neither a number nor a variable.
Examples
Success:
-(1, -1).
-(5, Result). (gives Result = -5)
-(-6.2, Result). (gives Result = 6.2)
Fail:
-(1, 0).
Error:
-(A, 6). (Error 4).
-(1, -1.0). (Error 5).
-(1.0, -1). (Error 5).
-(4 + 2, -6). (Error 24).
-(1, r). (Error 24).
See Also
is / 2