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rational(+Number, ?Result)

Converts Number into a rational number and unifies it with Result.
+Number
A number.
?Result
A variable or rational number.

Description

This predicate is used by the ECLiPSe compiler to expand evaluable arithmetic expressions. So the call to rational(Number, Result) is equivalent to 
    Result is rational(Number)
which should be preferred.

In coroutining mode, if Number is a free variable, the call to rational/2 is delayed until this variable is instantiated.

Fail Conditions

Fails if the result of the evaluation does not unify with Result.

Resatisfiable

No

Exceptions

(4) instantiation fault
Number is not instantiated (non-coroutining mode only).
(5) type error
Result is a number but not of type rational.
(24) number expected
Number is not of a numeric type.
(24) number expected
Result is neither a number nor a variable.

Examples

Success:
      rational(25, 25_1).
      rational(1.5, 3_2).
      rational(3_4,3_4).
      rational(9_12,3_4).
      rational(-6, Result).      (gives Result = -6_1)
Fail:
      rational(1, 2_1).
Error:
      rational(A, 1_3).                   (Error 4).
      rational(3, 3).                     (Error 5).
      rational(1, r).                     (Error 24).
      rational(4 + 2, 6_1).               (Error 24).

See Also

is / 2