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

# +(+Number1, +Number2, -Result)

Evaluates the sum Number1 + Number2 and unifies the resulting value with Result.

Number1
  A number.
Number2
  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 +(Number1, Number2, Result) is equivalent to

        Result is Number1 + Number2

which should be preferred for portability.

The result is of type breal if any of the arguments is a breal, else float if any of the arguments is a float, else rational if any of the arguments is a rational. Only when both arguments are integers is the result an integer.

In coroutining mode, if Number1 or Number2 are uninstantiated, the call to +/3 is delayed until these variables are instantiated.

### Modes and Determinism

- +(+, +, -) is det

### Exceptions

(4) instantiation fault
  Number1 or Number2 is not instantiated (non-coroutining mode only).
(5) type error
  Result is of a different type than the evaluation result.
(24) number expected
  Number1 or Number2 is not of a numeric type.
(24) number expected
  Result is neither a number nor a variable.

## Examples

    Success:
          +(5, 2, 7).
          +(5, -2.0, 3.0).
    Fail:
          +(1, 2, 7).
    Error:
          +(A, 2, 6).             (Error 4).
          +(1, 2, 3.0).           (Error 5).
          +(7 - 4, 2, 3).         (Error 24).
          +(5, 2, r).             (Error 24).

## See Also

is / 2