Prolog: Append elements of a list

Prolog provides append rule, to append the elements of a list.

1 ?- append([], [], X).
X = [].

2 ?- append([], [1, 2], X).
X = [1, 2].

3 ?- append([3, 4], [1, 2], X).
X = [3, 4, 1, 2].

4 ?- append([3, 4], [1, 2, 3], X).
X = [3, 4, 1, 2, 3].

You can even use the append method in other way.

5 ?- append(X, [1, 2, 3], [3, 4, 1, 2, 3]).
X = [3, 4] .

6 ?- append([3, X], [1, 2, 3], [3, 4, 1, 2, 3]).
X = 4.

7 ?- append([3, X], [Y, Z, 3], [3, 4, 1, 2, 3]).
X = 4,
Y = 1,
Z = 2.

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Prolog: convert list of characters to list of integers

Write a program that takes list of characters from a .. z and map a to 1, b t 2… and print the new list.

listDemo.pl

capital(a, 1).
capital(b, 2).
capital(c, 3).
capital(d, 4).
capital(e, 5).
capital(f, 6).
capital(g, 7).
capital(h, 8).
capital(i, 9).
capital(j, 10).
capital(k, 11).
capital(l, 12).
capital(m, 13).
capital(n, 14).
capital(o, 15).
capital(p, 16).
capital(q, 17).
capital(r, 18).
capital(s, 19).
capital(t, 20).
capital(u, 21).
capital(v, 22).
capital(w, 23).
capital(x, 24).
capital(y, 25).
capital(z, 26).

/*Default fallback case*/
capital(X, X).

alter([], []).
alter([Head1|Tail1], [Head2|Tail2]) :- capital(Head1, Head2), alter(Tail1, Tail2).

1 ?- consult(listDemo).
true.

2 ?- alter([1, 2, 3], X).
X = [1, 2, 3].

3 ?- alter([a, b, c], X).
X = [1, 2, 3] .

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