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

rem(+Number1, +Number2, -Result)

Evaluates the remainder Number1 rem Number2 and unifies the resulting value with Result.
Number1
Integer.
Number2
Integer.
Result
A variable or integer.

Description

This predicate is used by the ECLiPSe compiler to expand evaluable arithmetic expressions. So the call to rem(Number1, Number2, Result) is equivalent to
    Result is Number1 rem Number2
which should be preferred for portability.

The modulus operation computes the remainder corresponding to the truncating division //. The following relation always holds:

    X =:= (X rem Y) + (X // Y) * Y.
The result Result is either zero, or has the same sign as Number1. The absolute value of Result does not depend on the signs of the arguments.

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

See also the mod operation, whose result only differs when the arguments have opposite signs.

Modes and Determinism

Exceptions

(4) instantiation fault
Number1 or Number2 is not instantiated (non-coroutining mode only).
(5) type error
Result is a number but not an integer.
(5) type error
Number1 or Number2 is a number but not an integer.
(20) arithmetic exception
Illegal arithmetic operation: Number2 is zero
(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:
      X is 10 rem 3.		(gives X = 1)

      rem( 10,  3,  1).
      rem(-10,  3, -1).
      rem( 10, -3, -1).
      rem(-10, -3,  1).

      rem( 11,  3,  2).
Fail:
      rem(1, 2, 3).
Error:
      rem(A, 2, 6).              (Error 4).
      rem(6, 2.0, 3.0).          (Error 5).
      rem(2, 0, Result).         (Error 20).
      rem(4 + 2, 2, 12).         (Error 24).
      rem(5, 2, r).              (Error 24).

See Also

is / 2, // / 3, mod / 3