functional programming - OCaml - return a list containing all the elements in even position in the input list

Question

I am new to OCaml, and I am now trying to implement a function that returns a list containing all the elements in even position in the input list. For [1;2;3;5] returns [2;5] and for [1 3] returns [3]; and for ["i";"am";"new";"to";"ocaml"] returns ["am";"to"]. Hope someone can give me some suggestions to solve this problem.

Answer 1

There's nothing particularly OCaml-like in this problem. Most likely your main task is to learn to solve problems recursively.

The way to solve a problem recursively is to break it into two cases:

a. The input is so small the answer is ridiculously obvious.

b. The answer isn't so small, but you already have a function that works for (strictly) smaller inputs.

To solve the problem, you need to decide how to determine whether the input size is ridiculously small (a very short list), and how to use another function that works for smaller lists to solve your problem with a larger list. Then your own function is that other function (when called recursively).