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/(+Number1, +Number2, -Result)

Evaluates the quotient Number1 / Number2 and unifies the resulting value with Result.
Number1
A number.
Number2
A number.
Result
A variable or float (resp. rational).

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.

If both arguments are integers, then the result is of type float by default (coinciding with ISO-Prolog). This can be changed by switching the global flag 'prefer_rationals' to 'on': the result is then of rational type, and therefore precise. In practice, a better way to enforce a rational result is by explicitly converting one or both arguments to a rational before dividing, e.g. Z is rational(X)/Y.

The following table details the behaviour on zero-division, depending on the argument types. The exact result depends on the result's type ability to represent extreme values.

      -3 / 0                        -1.0Inf (negative infinity)
       0 / 0                        arithmetic exception
       3 / 0                         1.0Inf (positive infinity)

      -3.0 / 0.0                    -1.0Inf (negative infinity)
      -0.0 / 0.0                    arithmetic exception
       0.0 / 0.0                    arithmetic exception
       3.0 / 0.0                     1.0Inf (positive infinity)
      -3.0 / -0.0                    1.0Inf (positive infinity)
      -0.0 / -0.0                    arithmetic exception
       0.0 / -0.0                    arithmetic exception
       3.0 / -0.0                   -1.0Inf (negative infinity)

      rational(-3) / rational(0)    representation error
      rational( 0) / rational(0)    arithmetic exception
      rational( 3) / rational(0)    representation error

      breal(-3) / breal(0)          -1.0Inf__-1.0Inf (negative infinity)
      breal( 0) / breal(0)          -1.0Inf__1.0Inf (undefined)
      breal( 3) / breal(0)           1.0Inf__1.0Inf (positive infinity)
Dividing infinity by infinity yields the same result as 0/0.

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

Modes and Determinism

Exceptions

(4) instantiation fault
Number1 or Number2 is not instantiated (non-coroutining mode only).
(24) number expected
Number1 or Number2 is not of a numeric type.
(20) arithmetic exception
Illegal arithmetic operation: 0/0 or infinity/infinity

Examples

Success:
    /(10, 2, 5.0).
    /(10, -2.0, -5.0).
    /(9, 12, 3_4).      (with set_flag(prefer_rationals, on))
Fail:
    /(1, 2, 1.0).
    /(5, 2, r).
    /(6, 2, 3).
Error:
    /(A, 2, 6.0).            (Error 4).
    /(2, 0, Result).         (Error 20).
    /(4 + 2, 2, 12).         (Error 24).



See Also

is / 2, get_flag / 2, set_flag / 2