CODEWITHSUNDEEP
prolog
MeowMeow
MeowMeow

Reputation: 632

How to add to end of list in prolog

I am trying to add one item to the end of a list in prolog, but it keeps on failing. 

insertAtEnd(X,[ ],[X]).
insertAtEnd(X,[H|T],[H|Z]) :- insertAtEnd(X,T,Z).    

letters([a,b,c]).

I do not understand why this below does not work.

insertAtEnd(d,letters(Stored),letters(Stored)).

I am also attempting to store this list in the variable Stored throughout, but I am not sure if the above is correct way to proceed.

Upvotes: 9

Views: 24038

Answers (2)

kochav
kochav

Reputation: 51

you can use append and put your item as second list

like this:

insertAtEnd(X,Y,Z) :- append(Y,[X],Z).

Upvotes: 5

CapelliC
CapelliC

Reputation: 60024

Prolog implements a relational computation model, and variables can only be instantiated, not assigned. Try

?- letters(Stored),
   insertAtEnd(d, Stored, Updated),
   write(Updated).

Upvotes: 4

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