Using "cons" without the "::" operator ocaml

Question

Is there a way to construct lists in OCaml without using the :: operator?

For example, I know that normally elements would be concatenated as follows:

1::[2; 3; 4]

which produces [1; 2; 3; 4].

What I'm wondering is if it's possible to implement a method that takes

cons(1 cons(2 cons(3 cons (4 nil))))

and outputs the same result, as shown in the cons Wikipedia page.

Thank you.

Louis Roché · Accepted Answer · 2018-10-28 07:34:42Z

2

I think that you are looking for List.cons. Which allows you to do

# List.(cons 1 (cons 2 (cons 3 (cons 4 []))));;
- : int list = [1; 2; 3; 4]

answered Oct 28, 2018 at 7:34

Louis Roché

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2 Comments

Sean Over a year ago

Thank you! I was aware of the List.cons operator, but didn't know it could be used in this fashion. :)

Goswin von Brederlow Over a year ago

List.(...) just opens the List namespace temporarily. It's a short form of writing List.cons 1 (List.cons 2 (List.cons 3 (List.cons 4 []))) and more focused than writing open List. It's also great for using a modules infix operators like e.g. Vec2D.(a + b * s) without disrupting + everywhere.

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