list - How does Prolog handle this query -

this question has answer here:

considering following definition:

my_append([], l, l). my_append([h|t], l, [h|newtail]):- my_append(t, l, newtail).

and possible usage, , output:

?- my_append([1,2,5], [3,4], l). l = [1, 2, 5, 3, 4].

could me understanding how work?

this recursive function.

it splits first list head pieces , when empty takes second list , successively adds head front.

you can imagine multiple calls my_append follows:

my_append([1,2,5], [3,4], l)

which calls:

my_append([2,5], [3,4], l)

which calls:

my_append([5], [3,4], l)

which calls base case:

my_append([], [3,4], l)

this returned in reverse order follows:

l [3,4], l [5,3,4], l [2,5,3,4], l [1,2,5,3,4] , function ends.

KHS