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move length to lists

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This commit is contained in:
Vítor Santos Costa 2015-12-15 09:05:24 +00:00
parent a3a6386353
commit 83a3c52a75
2 changed files with 52 additions and 41 deletions
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52
pl/lists.yap
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@ -1,3 +1,13 @@
/**
* @file pl/lists.yap
* @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
* @date Thu Nov 19 09:54:00 2015
*
* @brief core lisy operations
*
* @ingroup lists
* @{
*/
:- system_module( '$_lists', [], []).
@ -88,4 +98,46 @@ lists:delete([Head|List], Elem, [Head|Residue]) :-
:- set_prolog_flag(source, false). % disable source.
% length of a list.
/** @pred length(? _L_,? _S_)
Unify the well-defined list _L_ with its length. The procedure can
be used to find the length of a pre-defined list, or to build a list
of length _S_.
*/
prolog:length(L, M) :-
'$skip_list'(L, M, M0, R),
( var(R) -> '$$_length'(R, M, M0) ;
R == []
).
%
% in case A1 is unbound or a difference list, things get tricky
%
'$$_length'(R, M, M0) :-
( var(M) -> '$$_length1'(R,M,M0)
; M >= M0 -> '$$_length2'(R,M,M0) ).
%
% Size is unbound, generate lists
%
'$$_length1'([], M, M).
'$$_length1'([_|L], O, N) :-
M is N + 1,
'$$_length1'(L, O, M).
%
% Size is bound, generate single list
%
'$$_length2'(NL, O, N) :-
( N =:= O -> NL = [];
M is N + 1, NL = [_|L], '$$_length2'(L, O, M) ).
%% @}

41
pl/sort.yap
View File

@ -37,47 +37,6 @@
*/
% length of a list.
/** @pred length(? _L_,? _S_)
Unify the well-defined list _L_ with its length. The procedure can
be used to find the length of a pre-defined list, or to build a list
of length _S_.
*/
length(L, M) :-
'$skip_list'(L, M, M0, R),
( var(R) -> '$$_length'(R, M, M0) ;
R == []
).
%
% in case A1 is unbound or a difference list, things get tricky
%
'$$_length'(R, M, M0) :-
( var(M) -> '$$_length1'(R,M,M0)
; M >= M0 -> '$$_length2'(R,M,M0) ).
%
% Size is unbound, generate lists
%
'$$_length1'([], M, M).
'$$_length1'([_|L], O, N) :-
M is N + 1,
'$$_length1'(L, O, M).
%
% Size is bound, generate single list
%
'$$_length2'(NL, O, N) :-
( N =:= O -> NL = [];
M is N + 1, NL = [_|L], '$$_length2'(L, O, M) ).
/** @pred sort(+ _L_,- _S_) is iso