Addition of element in a list of record (OCaml)

Question

I have a list of record :

list_clients = [{name = "c6"; number = 9}; {name = "c12"; number = 3}; {name = "c17"; number = 6};]

I would like to simply make the sum of all the "number" of each record.

What is the best way? I'm quite beginner with OCaml.

score 6 · Accepted Answer · answered Jun 10 '13 at 04:02

6

Use a fold:

List.fold_left (fun acc nxt -> nxt.number+acc) 0 list_clients

This takes every element in the list, grabs said element's 'number' field, and adds it to the total thus far, passing along the result.

answered Jun 10 '13 at 04:02

Charles Marsh

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Thanks a lot!! It's exactly what I was trying to reproduce. – moumoute6919 Jun 10 '13 at 21:07

score 3 · Answer 2 · answered Jun 10 '13 at 10:19

A bit more explanation about Charles Marsh's answer.

List.fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a takes a function f, an element a and a list [b1; b2; ...; bn] and computes f (... (f (f a b1) b2) ...) bn. It allows you you to easily compute the sum of the elements of a list: List.fold_left (+) 0 l, its maximum element: List.fold_left max (List.hd l) l or anything where you need to go through every element of the list, aggregating it with the previous result.

Addition of element in a list of record (OCaml)

2 Answers2