[ 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

- -(+, -) is det

### 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