F# explicit match vs function syntax

syntax f#

Benjol · Dec 3, 2009 · Viewed 15.6k times · Source

Sorry about the vague title, but part of this question is what these two syntax styles are called:

let foo1 x = 
    match x with
    | 1 -> "one"
    | _ -> "not one"

let foo2 = function 
    | 1 -> "one" 
    | _ -> "not one"

The other part is what difference there is between the two, and when I would want to use one or the other?

Answer

The pro for the second syntax is that when used in a lambda, it could be a bit more terse and readable.

List.map (fun x -> match x with | 1 -> "one" | _ -> "not one") [0;1;2;3;1]

List.map (function 1 -> "one" | _ -> "not one") [0;1;2;3;1]