Modul Bits

Jan Burse, erstellt 03. Mär 2020
/**
* We provide a couple of additional bitwise operations. The evaluable
* functions setbit/2 and clearbit/2 update the given integer in a
* more efficient way than would be possible with existing logical
* and shift operations:
*
* Examples:
* ?- testbit(-100,3).
* Yes
* ?- testbit(100,3).
* No
*
* The predicate testbit/2 tests a particular bit in a given integer, again
* the implementation is more efficient than would be possible with
* existing logical, shift and test operations. The evaluable functions
* and the predicate require a positive or zero shift.
*
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* provided by XLOG Technologies GmbH.
*
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*
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*
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*/
:- package(library(jekmin/reference/misc)).
:- use_package(foreign(jekmin/reference/misc)).
:- module(bits, []).
/**
* setbit(X, Y, Z):
* If X and Y are integers than the function returns X \/ (1 << Y).
*/
:- public setbit/3.
:- special(setbit/3, 'SupplementBits', 3).
/**
* clearbit(X, Y, Z):
* If X and Y are integers than the function returns X /\ \ (1 << Y).
*/
:- public clearbit/3.
:- special(clearbit/3, 'SupplementBits', 4).
/**
* testbit(X, Y):
* The predicate succeeds when X /\ (1 << Y) =\= 0.
*/
:- public testbit/2.
:- special(testbit/2, 'SpecialBits', 0).

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