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truncate, i64truncate

Library: fbudf

Added in: 1.0 (Win), 1.5 (Linux)

Changed in: 1.5, 2.1.3

Better alternative: Internal function TRUNC()

Description

These functions return the whole-number portion of their (scaled numeric/decimal) argument. They do not work with floats or doubles.

Result type: INTEGER / NUMERIC(18)

Syntax

 truncate    (number)
 i64truncate (bignumber)

Caution: Both functions round to the nearest whole number that is lower than or equal to the argument. This means that negative numbers are also "truncated" downward. For instance, truncate(-2.37) returns -3. The internal function TRUNC, available since Firebird 2.1, always truncates toward zero.

Bug alert: Contrary to what's mentioned above, in versions 2.1, 2.1.1 and 2.1.2 anything between -1 and 0 is truncated to 0. This anomaly has been corrected in Firebird 2.1.3 and above.

Declarations

In Firebird 1.0.x, the entry point for both functions is truncate:

 DECLARE EXTERNAL FUNCTION Truncate
   INT BY DESCRIPTOR, INT BY DESCRIPTOR
   RETURNS PARAMETER 2
   ENTRY_POINT 'truncate' MODULE_NAME 'fbudf'

 DECLARE EXTERNAL FUNCTION i64Truncate
   NUMERIC(18) BY DESCRIPTOR, NUMERIC(18) BY DESCRIPTOR
   RETURNS PARAMETER 2
   ENTRY_POINT 'truncate' MODULE_NAME 'fbudf'

In Firebird 1.5, the entry point has been renamed to fbtruncate:

 DECLARE EXTERNAL FUNCTION Truncate
   INT BY DESCRIPTOR, INT BY DESCRIPTOR
   RETURNS PARAMETER 2
   ENTRY_POINT 'fbtruncate' MODULE_NAME 'fbudf'

 DECLARE EXTERNAL FUNCTION i64Truncate
   NUMERIC(18) BY DESCRIPTOR, NUMERIC(18) BY DESCRIPTOR
   RETURNS PARAMETER 2
   ENTRY_POINT 'fbtruncate' MODULE_NAME 'fbudf'

If you move an existing database from Firebird 1.0.x to 1.5 or higher, drop any existing *round and *truncate declarations and declare them anew, using the updated entry point names. From Firebird 2.0 onward you can also perform this update with ALTER EXTERNAL FUNCTION.

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