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truncate(+Number, -Result)

Unifies Result with the closest integer value between 0 and Number, and of the same numeric type as Number.
Number
A number.
Result
A variable or number.

Description

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

This operation works on all numeric types. The result value is the closest integral value that lies between 0 and Number (rounding towards zero).

The result type is the same as the argument type. To convert the type to integer, use integer/2.

In coroutining mode, if Number is uninstantiated, the call to truncate/2 is delayed until this variable is instantiated.

Modes and Determinism

Exceptions

(4) instantiation fault
Number is not instantiated (non-coroutining mode only).
(24) number expected
Number is not of a numeric type.

Examples

Success:
      X is truncate(1.8).	   (gives Result = 1.0)

      truncate(1.8, 1.0).
      truncate(-1.8, -1.0).
      truncate(5, 5).
      truncate(-6.4, Result).      (gives Result = -6.0)
Fail:
      truncate(1.0, 0.0).
      truncate(0.5, 0).
      truncate(1, r).
Error:
      truncate(A, 6.0).                   (Error 4).
      truncate(4 + 2.3, 6.0).             (Error 24).

See Also

is / 2, floor / 2, ceiling / 2, round / 2, integer / 2, fix / 2