Question

I’m trying to learn how to think in a functional programming way, for this, I’m trying to learn Erlang and solving easy problems from codingbat. I came with the common problem of comparing elements inside a list. For example, compare a value of the i-th position element with the value of the i+1-th position of the list. So, I have been thinking and searching how to do this in a functional way in Erlang (or any functional language).

Please, be gentle with me, I’m very newb in this functional world, but I want to learn

Thanks in advance

Answer 1

Define a list:

L = [1,2,3,4,4,5,6]

Define a function f, which takes a list

• If it matches a list of one element or an empty list, return the empty list
• If it matches the first element and the second element then take the first element and construct a new list by calling the rest of the list recursivly
• Otherwise skip the first element of the list.

In Erlang code

f ([]) -> [];
f ([_]) -> [];
f ([X, X|Rest]) -> [X | f(Rest)];
f ([_|Rest]) -> f(Rest).

Apply function

f(L)

This should work… haven’t compiled and run it but it should get you started. Also in case you need to do modifications to it to behave differently.

Welcome to Erlang 😉