Is there something like List.init, but of the form "int -> 'T -> 'T list" instead?

I am looking for a way to try to simplify the following expression, which looks ugly, IM开发者_运维百科O:

List.map (fun _ -> generateIndividual()) [1..popSize]

I found about List.init, but it still isn't really what I am looking for:

List.init popSize (fun x -> generateIndividual())

It'd be perfect gave it not an argument to the lambda expression. It'd be perfect this way:

List.init popSize generateIndividual()

Is there something in the F# library that'd help me clean this up?

Thanks

Thanks to the fact that unit(void) is also a type you can do this:

List.init popSize (ignore >> generateIndividual)

Not really. The nearest solution would be to alter the definition of your generateIndividual function so that it accepts a value of any type (rather than just the value of the type unit) and discards it:

let generateIndividual _ = ...

Then you could write:

List.init popSize generateIndividual

Another solution is to use a list comprehension:

[for _ in 1..popSize -> generateIndividual()]

You could do:

[ for i = 1 to popSize do 
      yield generateIndividual() ]

How about this?

let generateIndividual dummy = 4
let popSize = 10
let lst = List.init popSize generateIndividual

You can create an extension like this:

module List =
    let init2 count f = List.init count (fun _ -> f())

You can then call it like this:

List.init2 5 generateIndividual

I know, late and all, but:

1. This solution is as short as you'll get,

2. Unlike ebb's (which you've chosen), this one will execute side-effects once:

   (fun a -> Array.create a >> List.ofArray)

The type is exactly (int -> 'a -> 'a list), only disadvantage is conversion from Array to List, but this is still a bit better performance-wise than converting Seq to List (which is what done by list expressions).