[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

# +(+Number, -Result)

Checks if Number is a number and unifies it 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).
          +(1.0, 1).                 (Error 5).
          +(1, 1.0).                 (Error 5).
          +(4 + 2, 6).               (Error 24).
          +(1, r).                   (Error 24).

## See Also

is / 2