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yap-6.3/LGPL/chr/hprolog.yap
vsc 4d94446c25 port of LGPLed CHR
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1416 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
2005-10-28 17:41:30 +00:00

197 lines
4.3 KiB
Prolog

:- module(hprolog,
[ %prolog_flag/3, % +Flag, -Old, +New
append_lists/2, % +ListOfLists, -List
%nth/3, % ?Index, ?List, ?Element
%substitute/4, % +OldVal, +OldList, +NewVal, -NewList
memberchk_eq/2, % +Val, +List
intersect_eq/3, % +List1, +List2, -Intersection
list_difference_eq/3, % +List, -Subtract, -Rest
take/3, % +N, +List, -FirstElements
max_go_list/2, % +List, -Max
or_list/2, % +ListOfInts, -BitwiseOr
%sublist/2,
%min_list/2,
chr_delete/3,
strip_attributes/2,
restore_attributes/2
]).
:- use_module(library(lists)).
% prolog_flag(+Flag, -Old, +New)
%
% Combine ISO prolog flag reading and writing
/*
prolog_flag(Flag, Old, New) :-
current_prolog_flag(Flag, Old),
( Old == New
-> true
; set_prolog_flag(Flag, New)
).
*/
/*******************************
* MORE LIST OPERATIONS *
*******************************/
% append_lists(+ListOfLists, -List)
%
% Convert a one-level nested list into a flat one. E.g.
% append_lists([[a,b], [c]], X) --> X = [a,b,c]. See also
% flatten/3.
append_lists([],[]).
append_lists([X|Xs],L) :-
append(X,T,L),
append_lists(Xs,T).
% nth(?Index, ?List, ?Element)
%
% Same as nth1/3
nth(Index, List, Element) :-
nth1(Index, List, Element).
% substitute(+OldVal, +OldList, +NewVal, -NewList)
%
% Substitute OldVal by NewVal in OldList and unify the result
% with NewList. JW: Shouldn't this be called substitute_eq/4?
substitute(_, [], _, []) :- ! .
substitute(X, [U|Us], Y, [V|Vs]) :-
( X == U
-> V = Y,
substitute(X, Us, Y, Vs)
; V = U,
substitute(X, Us, Y, Vs)
).
% memberchk_eq(+Val, +List)
%
% Deterministic check of membership using == rather than
% unification.
memberchk_eq(X, [Y|Ys]) :-
( X == Y
-> true
; memberchk_eq(X, Ys)
).
% list_difference_eq(+List, -Subtract, -Rest)
%
% Delete all elements of Subtract from List and unify the result
% with Rest. Element comparision is done using ==/2.
list_difference_eq([],_,[]).
list_difference_eq([X|Xs],Ys,L) :-
( memberchk_eq(X,Ys)
-> list_difference_eq(Xs,Ys,L)
; L = [X|T],
list_difference_eq(Xs,Ys,T)
).
% intersect_eq(+List1, +List2, -Intersection)
%
% Determine the intersection of two lists without unifying values.
intersect_eq([], _, []).
intersect_eq([X|Xs], Ys, L) :-
( memberchk_eq(X, Ys)
-> L = [X|T],
intersect_eq(Xs, Ys, T)
; intersect_eq(Xs, Ys, L)
).
% take(+N, +List, -FirstElements)
%
% Take the first N elements from List and unify this with
% FirstElements. The definition is based on the GNU-Prolog lists
% library. Implementation by Jan Wielemaker.
take(0, _, []) :- !.
take(N, [H|TA], [H|TB]) :-
N > 0,
N2 is N - 1,
take(N2, TA, TB).
% max_go_list(+List, -Max)
%
% Return the maximum of List in the standard order of terms.
max_go_list([H|T], Max) :-
max_go_list(T, H, Max).
max_go_list([], Max, Max).
max_go_list([H|T], X, Max) :-
( H @=< X
-> max_go_list(T, X, Max)
; max_go_list(T, H, Max)
).
% or_list(+ListOfInts, -BitwiseOr)
%
% Do a bitwise disjuction over all integer members of ListOfInts.
or_list(L, Or) :-
or_list(L, 0, Or).
or_list([], Or, Or).
or_list([H|T], Or0, Or) :-
Or1 is H \/ Or0,
or_list(T, Or1, Or).
sublist(L, L).
sublist(Sub, [H|T]) :-
'$sublist1'(T, H, Sub).
'$sublist1'(Sub, _, Sub).
'$sublist1'([H|T], _, Sub) :-
'$sublist1'(T, H, Sub).
'$sublist1'([H|T], X, [X|Sub]) :-
'$sublist1'(T, H, Sub).
min_list([H|T], Min) :-
'$min_list1'(T, H, Min).
'$min_list1'([], Min, Min).
'$min_list1'([H|T], X, Min) :-
( H>=X ->
'$min_list1'(T, X, Min)
; '$min_list1'(T, H, Min)
).
chr_delete([], _, []).
chr_delete([H|T], X, L) :-
( H==X ->
chr_delete(T, X, L)
; L=[H|RT],
chr_delete(T, X, RT)
).
strip_attributes([],[]).
strip_attributes([V|R],[V2|R2]) :-
( attvar(V) ->
get_attrs(V,VAttrs),
remove_attrs(V,VAttrs,V2)
; V2 = []
),
strip_attributes(R,R2).
remove_attrs(_V,[],[]).
remove_attrs(V,att(X,Y,OtherAttrs),[(X,Y)|R]) :-
del_attr(V,X),
remove_attrs(V,OtherAttrs,R).
restore_attributes([],[]).
restore_attributes([_V|R],[[]|R2]) :-
restore_attributes(R,R2).
restore_attributes([V|R],[[(X,Y)|RVAttr]|R2]) :-
put_attr(V,X,Y),
restore_attributes([V|R],[RVAttr|R2]).