F# List.first deprecated, what is the new method

Question

I am porting over some old F# code from CTP 1.9.6.8

The code uses List.first:

List.first (fun x -> if x.Date = d then Some(x) else None)

List.first has been deprecated. What is the current method used to achieve the same functionality.

I have reviewed the release notes and could not find any specific reference to the change.

Any help would be greatly appreciated.

Answer 1

Try List.pick

List.pick (fun x -> if x.Date = d then Some(x) else None)

Answer 2

@JaredPar is right.

Note that the F# library docs are here:

http://msdn.microsoft.com/en-us/library/ee353567(VS.100).aspx

and specifically the List module is here:

http://msdn.microsoft.com/en-us/library/ee353738(VS.100).aspx

and searching for 'first' on that page reveals the usual suspects.

Answer 3

What @JaredPar suggested with List.pick is right, though it would raise a KeyNotFoundException if the element does not exist.

You can use List.tryPick if you want an option to be returned in both cases, found and not found.

It's use is the same:

List.tryPick (fun x -> if x.Date = d then Some(x) else None)