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-(+Number1, +Number2, -Result)

Evaluates the difference Number1 - Number2 and unifies the resulting value with Result.
A number.
A number.
A variable or a number.


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


(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.


      -(5, 2, 3).            (gives Result = 3)
      -(5, -2.0, Result).    (gives Result = 7.0)
      -(1, 2, 3).
      -(A, 2, 6).             (Error 4).
      -(1, 2, 3.0).           (Error 5).
      -(4 + 1, 2, 3).         (Error 24).
      -(5, 2, r).             (Error 24).

See Also

is / 2