Modul Bits

Jan Burse, erstellt 15. Sep 2018
/**
* We provide a couple of additional bitwise operations. The evaluable
* functions bitcount/1, bitlength/1 and lowestsetbit/1 deal with the
* determination of certain bits of the given integer. The implementation
* is more efficient than would be possible with existing logical,
* shift and test operations.
*
* Examples:
* bitlength(333) --> 9
*
* 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. 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.
*
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
*
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* Technologies GmbH. If the company was not the originator of some
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*
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* for execution provided this comment remains unchanged.
*
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
*
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
*/
:- package(library(jekmin/reference/misc)).
:- use_package(foreign(jekmin/reference/misc)).
:- module(bits, []).
/**
* bitcount(X, N):
* Predicate succeeds in N with the number of non-zero bits of X.
*/
:- public bitcount/2.
:- special(bitcount/2, 'SupplementBits', 0).
/**
* bitlength(X, N):
* Predicate succeeds in N with the highest non-zero bit of X.
*/
:- public bitlength/2.
:- special(bitlength/2, 'SupplementBits', 1).
/**
* lowestsetbit(X, N):
* Predicate succeeds in N with the lowest non-zero bit of X.
*/
:- public lowestsetbit/2.
:- special(lowestsetbit/2, 'SupplementBits', 2).
/**
* setbit(X, Y, Z):
* The predicate succeeds in Z with Y \/ (1 << X).
*/
:- public setbit/3.
:- special(setbit/3, 'SupplementBits', 3).
/**
* clearbit(X, Y, Z):
* The predicate succeeds in Z with Y /\ \ (1 << X).
*/
:- public clearbit/3.
:- special(clearbit/3, 'SupplementBits', 4).
/**
* testbit(X, Y):
* The predicate succeeds when Y /\ (1 << X) =\= 0.
*/
:- public testbit/2.
:- special(testbit/2, 'SpecialBits', 0).

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