[ 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 uninstantiated, the call to -/2 is
delayed until this variable is instantiated.

### Modes and Determinism

### 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