Question

Write a program that deletes vowels (String, NoVowelsString) that deletes all vowels from a given string.

So far I’ve got the condition vowel(X):- member(X,[a,e,i,o,u]). Then I thought of the one that deletes all the elements from the other list:

delete2([],L1,L1).
delete2([H|T],L1,L3) :-
   delete2(H,L1,R2),
   delete2(T,R2,L3).

So having these two I thought that I could put a condition to those elements being deleted that they have to be a member of [a,e,i,o,u]. Though I still haven’t got anywhere.

Answer 1

Here is the code

deleteV([H|T],R):-member(H,[a,e,i,o,u]),deleteV(T,R),!.
deleteV([H|T],[H|R]):-deleteV(T,R),!.
deleteV([],[]).

What it does?
First it question itself?It’s the head a vowel
Yes->We ignore it.
No->We need it.
If it finds an empty list, it constructs the result list, and when returning from backtracking it appends the consonats in front.
This code was tested in SWIProlog.