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

# 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

- truncate(+, -) is det

### Exceptions

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

## 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).
    Error:
          truncate(A, 6.0).                   (Error 4).
          truncate(0.5, 0).                   (Error 5).
          truncate(1, r).                     (Error 24).
          truncate(4 + 2.3, 6.0).             (Error 24).

## See Also

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