====== Npda ======
{{tag>NPDA}}
===== Description =====
Specializing an NPDA


**Source**:  The Art of Prolog
===== Download =====
Program source code: {{npda.pl}}

===== Listing =====
<code prolog>
    program(npda,[(accept(Xs1) :-  initial(Q1), accept(Xs1,Q1,[ ])),

        (accept([_],Q2,S2) :-  delta(Q2,_,S2,Q12,S12),

        accept(_,Q12,S12)), (accept([ ],_,[ ]) :-  true)]).



    should_unfold(initial(_)).

    should_unfold(final(_)).

    should_unfold(delta(_,_,_,_,_)).



    should_fold(accept(Q,Xs,Q1),palindrome(Q,Xs,Q1)).

    should_fold(accept(Xs),palindrome(Xs)).



%    Program 18.4: Specializing an 

PDA

</code>
===== Comments =====