Extension of arg/3

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Detailed Description

An extension of arg/3 that supports backtracking through a term

• *This library extends arg/3 by supporting backtracking through *arguments and access to sub-arguments,
• • arg0/3
  • args/3
  • args0/3
  • genarg/3
  • genarg0/3
  • path_arg/3
• *It is based on the Quintus Prolog public domain library Except for *project, all predicates use the arg/3 argument pattern 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 that implements arg/3 and genarg/3

---

Class Documentation

genarg/3

class genarg/3

genarg( ?Index, +Term , -Arg )

Similar to arg/3 , but it can also backtrack through T's arguments, that is:

?- arg:genarg(I, f(a,b), A).
A = a,
I = 1.
;
A = b,
I = 2.

Note: SWI-Prolog defines arg/3 as genarg/3

arg0/3

class arg0/3

arg0( +_Index_, +_Term_ , -_Arg_ )

• Similar to arg/3 , but arg0(0,_T_,_F_) unifies F with T's principal functor:

?- arg0(0, f(a,b), A).
A = arg0.
?- arg0(1, f(a,b), A).
A = arg0.
?- arg0(2, f(a,b), A).
A = .

genarg0/3

class genarg0/3

genarg0( +_Index_, +_Term_ , -_Arg_ )

• Similar to genarg/3 , but genarg0(0,_T_,_F_) unifies F with T's principal functor:

  ?- genarg0(I,f(a,b),A).
  A = genarg0,
  I = 0 ? ;
  A = genarg0,
  I = 1 ? ;
  A = ,
  I = 2.

args/3

class args/3

args( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )

• Succeeds if ListOfArgs unifies with the application of genarg/3 to every element of ListOfTerms

It corresponds to calling maplist/3 on genarg/3 :

args( I, Ts, As) :-
    maplist( genarg(I), Ts, As).

Notice that unification allows ListOfArgs to be bound, eg:

?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
X1 = X2 = X3 = X4 = 1.

args0/3

class args0/3

args0( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )

args0( +_ListOfTerms_ , +_Index_, -_ListOfArgs_ )

• Succeeds if ListOfArgs unifies with the application of genarg0/3 to every element of ListOfTerms

It corresponds to calling maplist/3 on genarg0/3 :

args( I, Ts, As) :-
    maplist( genarg0(I), Ts, As).

Notice that unification allows ListOfArgs to be bound, eg:

?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
X1 = X2 = X3 = X4 = 1.

• Succeeds if ListOfArgs unifies with the application of genarg0/3 to every element of ListOfTerms

It corresponds to calling args0/3 but with a different order

path_arg/3

class path_arg/3

path_arg( +_Path_ , +_Term_, -_Arg_ )

• 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
• Notice that it can be used to enumerate all possible paths in a term

Function Documentation

Yap_InitInlines()

void Yap_InitInlines

(

void

)

Definition at line 1194 of file inlines.c.

Functions
void	Yap_InitInlines (void)