F# explicit match vs function syntax

Question

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\"
    |         


        

Answer 1

The function version is a short hand for the full match syntax in the special case where the match statement is the entire function and the function only has a single argument (tuples count as one). If you want to have two arguments then you need to use the full match syntax*. You can see this in the types of the following two functions.

//val match_test : string -> string -> string
let match_test x y = match x, y with
                        | "A", _ -> "Hello A"
                        | _, "B" -> "Hello B"
                        | _ -> "Hello ??"

//val function_test : string * string -> string                   
let function_test = function
                        | "A", _ -> "Hello A"
                        | _, "B" -> "Hello B"
                        | _ -> "Hello ??"

As you can see match version takes two separate arguments whereas the function version takes a single tupled argument. I use the function version for most single argument functions since I find the function syntax looks cleaner.

*If you really wanted to you can get the function version to have the right type signature but it looks pretty ugly in my opinion - see example below.

//val function_match_equivalent : string -> string -> string
let function_match_equivalent x y = (x, y) |> function
                                                | "A", _ -> "Hello A"
                                                | _, "B" -> "Hello B"
                                                | _ -> "Hello ??"

Answer 2

This is an old question but I will throw my $0.02.

In general I like better the match version since I come from the Python world where "explicit is better than implicit."

Of course if type information on the parameter is needed the function version cannot be used.

OTOH I like the argument made by Stringer so I will start to use function in simple lambdas.