Editing Tail call (section)

===Example code===
{|
|-
|<syntaxhighlight lang="prolog">
% Prolog, tail recursive modulo cons:
partition([], _, [], []).
partition([X|Xs], Pivot, [X|Rest], Bigs) :-
  X @< Pivot, !,
  partition(Xs, Pivot, Rest, Bigs).
partition([X|Xs], Pivot, Smalls, [X|Rest]) :-
  partition(Xs, Pivot, Smalls, Rest).
</syntaxhighlight>
|<syntaxhighlight lang="haskell">
-- In Haskell, guarded recursion:
partition [] _ = ([],[])
partition (x:xs) p 
        | x < p     = (x:a,b)
        | otherwise = (a,x:b)
   where
      (a,b) = partition xs p

</syntaxhighlight>
|-
|<syntaxhighlight lang="prolog">
% Prolog, with explicit unifications:
%     non-tail recursive translation:
partition([], _, [], []).
partition(L, Pivot, Smalls, Bigs) :- L=[X|Xs],
 (  X @< Pivot
 -> partition(Xs,Pivot,Rest,Bigs), Smalls=[X|Rest]
 ;  partition(Xs,Pivot,Smalls,Rest), Bigs=[X|Rest]
 ).
</syntaxhighlight>
|<syntaxhighlight lang="prolog">
% Prolog, with explicit unifications:
%     tail-recursive translation:
partition([], _, [], []).
partition(L, Pivot, Smalls, Bigs) :- L=[X|Xs],
 (  X @< Pivot
 -> Smalls=[X|Rest], partition(Xs,Pivot,Rest,Bigs)
 ;  Bigs=[X|Rest], partition(Xs,Pivot,Smalls,Rest)
 ).

</syntaxhighlight>
|}

Thus in tail-recursive translation such a call is transformed into first creating a new [[Node (computer science)|list node]] and setting its <code>first</code> field, and ''then'' making the tail call with the pointer to the node's <code>rest</code> field as argument, to be filled recursively. The same effect is achieved when the recursion is ''guarded'' under a lazily evaluated data constructor, which is automatically achieved in lazy programming languages like Haskell.