168 lines
3.3 KiB
Prolog
168 lines
3.3 KiB
Prolog
/**
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* @file arg.yap
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* @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
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* @date Tue Nov 17 01:08:55 2015
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*
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* @brief
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*/
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/**
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*
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@defgroup args Term Argument Manipulation.
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@ingroup @library
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@{
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Extends arg/3 by including backtracking through arguments and access
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to sub-arguments,
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- arg0/3
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- args/3
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- args0/3
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- genarg/3
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- genarg0/3
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- path_arg/3
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It is based on the Quintus Prolog arg library. Except for project, all
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predicates use the arg/3 argument pattern.
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This file has been included in the YAP library by Vitor Santos Costa, 2008. No error checking is actuallly performed within the package: this left to the C-code thaat implements arg``/3 and
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genarg/3.
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*/
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:- module(arg,
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[
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genarg/3,
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arg0/3,
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genarg0/3,
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args/3,
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args0/3,
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% project/3
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path_arg/3
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]).
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/**
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* @pred arg0( +_Index_, +_Term_ , -_Arg_ )
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*
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* Similar to arg/3, but `arg0(0,_T_,_F_)` unifies _F_ with _T_'s principal functor:
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~~~~~~~~~
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?- arg0(0, f(a,b), A).
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A = f.
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?- arg0(1, f(a,b), A).
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A = a.
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?- arg0(2, f(a,b), A).
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A = b.
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~~~~~~~~~
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*/
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arg0(0,T,A) :- !,
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functor(T,A,_).
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arg0(I,T,A) :-
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arg(I,T,A).
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/**
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* @pred genarg0( +_Index_, +_Term_ , -_Arg_ )
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*
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* Similar to genarg/3, but `genarg0(0,_T_,_F_)` unifies _F_ with _T_'s principal functor:
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~~~~~~~~~
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?- genarg0(I,f(a,b),A).
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A = f,
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I = 0 ? ;
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A = a,
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I = 1 ? ;
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A = b,
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I = 2.
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~~~~~~~~~
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*/
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genarg0(I,T,A) :-
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nonvar(I), !,
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arg0(I,T,A).
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genarg0(0,T,A) :-
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functor(T,A,_).
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genarg0(I,T,A) :-
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genarg(I,T,A).
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/**
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* @pred args( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )
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*
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* Succeeds if _ListOfArgs_ unifies with the application of genarg/3 to every element of _ListOfTerms_.
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It corresponds to calling maplist/3 on genarg/3:
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~~~~~~~~~
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args( I, Ts, As) :-
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maplist( genarg(I), Ts, As).
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~~~~~~~~~
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Notice that unification allows _ListOfArgs_ to be bound, eg:
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~~~~~~~~~
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?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
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X1 = X2 = X3 = X4 = 1.
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~~~~~~~~~
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*/
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args(_,[],[]).
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args(I,[T|List],[A|ArgList]) :-
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genarg(I, T, A),
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args(I, List, ArgList).
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/**
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* @pred args0( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )
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*
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* Succeeds if _ListOfArgs_ unifies with the application of genarg0/3 to every element of _ListOfTerms_.
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It corresponds to calling maplist/3 on genarg0/3:
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~~~~~~~~~
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args( I, Ts, As) :-
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maplist( genarg0(I), Ts, As).
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~~~~~~~~~
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Notice that unification allows _ListOfArgs_ to be bound, eg:
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~~~~~~~~~
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?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
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X1 = X2 = X3 = X4 = 1.
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~~~~~~~~~
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*/
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args0(_,[],[]).
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args0(I,[T|List],[A|ArgList]) :-
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genarg(I, T, A),
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args0(I, List, ArgList).
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/**
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* @pred args0( +_ListOfTerms_ , +_Index_, -_ListOfArgs_ )
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*
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* Succeeds if _ListOfArgs_ unifies with the application of genarg0/3 to every element of _ListOfTerms_.
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It corresponds to calling args0/3 but with a different order.
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*/
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project(Terms, Index, Args) :-
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args0(Index, Terms, Args).
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% no error checking here!
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/**
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* @pred path_arg( +_Path_ , +_Term_, -_Arg_ )
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*
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* Succeeds if _Path_ is empty and _Arg unifies with _Term_, or if _Path_ is a list with _Head_ and _Tail_, genarg/3 succeeds on the current term, and path_arg/3 succeeds on its argument.
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*
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* Notice that it can be used to enumerate all possible paths in a term.
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*/
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path_arg([], Term, Term).
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path_arg([Index|Indices], Term, SubTerm) :-
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genarg(Index, Term, Arg),
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path_arg(Indices, Arg, SubTerm).
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%%% @}
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/** @} */
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