Introduction

Finding the index of the first non-zero element in a list is a common task in programming. In this tutorial, we will discuss how to find the index of the first non-zero element in a list using the Ocaml programming language. We will look at a few different methods for finding the index of the first non-zero element in a list, including using the List.find_index function, using a recursive function, and using a loop. We will also discuss the advantages and disadvantages of each approach. By the end of this tutorial, you should have a good understanding of how to find the index of the first non-zero element in a list using Ocaml.

Solution

let rec find_index lst =
match lst with
| [] -> -1
| hd::tl -> if hd = 0 then find_index tl else 0;;

class c = object (self)
  method f i = function
    | x::_ when x <> 0 -> i
    | _::xs -> self#f (i+1) xs
    | [] -> failwith "Got the answer from StackOverflow"
end
;;

(new c)#f 0 [0;0;1;2;0;4;5;6];;

Solved: How to Find Index of First Non-Zero Element in a List (Language – Ocaml)

Finding the index of the first non-zero element in a list can be a tricky task. Fortunately, Ocaml provides a few different ways to accomplish this. In this article, we’ll discuss three different methods for finding the index of the first non-zero element in a list.

Method 1: Using List.find_index

The List.find_index function is a built-in Ocaml function that takes a predicate and a list as arguments and returns the index of the first element in the list that satisfies the predicate. To find the index of the first non-zero element in a list, we can use the following code:

let index = List.find_index (fun x -> x <> 0) list

This code will return the index of the first non-zero element in the list, or -1 if no such element exists.

Method 2: Using List.fold_left

Another way to find the index of the first non-zero element in a list is to use the List.fold_left function. This function takes a function, an initial value, and a list as arguments and applies the function to each element of the list, starting from the left. To find the index of the first non-zero element in a list, we can use the following code:

let index = List.fold_left (fun acc x -> if x <> 0 then Some acc else None) None list

This code will return the index of the first non-zero element in the list, or None if no such element exists.

Method 3: Using List.iteri

The List.iteri function is a built-in Ocaml function that takes a function and a list as arguments and applies the function to each element of the list, along with its index. To find the index of the first non-zero element in a list, we can use the following code:

let index = ref None
List.iteri (fun i x -> if x <> 0 then index := Some i) list

This code will set the index variable to the index of the first non-zero element in the list, or None if no such element exists.

Conclusion

In this article, we discussed three different methods for finding the index of the first non-zero element in a list. Each method has its own advantages and disadvantages, so it’s important to choose the one that best suits your needs. With the right approach, finding the index of the first non-zero element in a list can be a simple task.