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Request: Slicing for other containers like ResizeArray
f#

I would like to request slicing syntax for other containers like ResizeArray.
Right now you can get it while implementing GetSlice member with a type extension like below but it would be nice to have it in the library as standard, same goes for standard operators for pointers arithmetic

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let inline array_sub (arr:ResizeArray<'a>) (start:int) (len:int) =
    let len1 = if len < 0 then 0 else len
    let dst = new ResizeArray<'a> (len1)
    for i = 0 to len - 1 do 
        dst.Add (arr.[start + i])
    dst
    
type System.Collections.Generic.List<'a> with
    member inline l.GetSlice (start, finish) =
        let start  = match start with None -> 0 | Some n -> n
        let finish = match finish with None -> l.Count - 1 | Some n -> n
        array_sub l start (finish - start + 1)
.

Thanks, this is a great suggestion. It turns out that because slicing syntax is a syntactic translation, you can add slicing syntax via an extension member:

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type System.Collections.Generic.List<'T> with 
    member x.GetSlice(a,b) = 
        let a = defaultArg a 0
        let b = defaultArg b (x.Count-1)
        [| for i in a .. b -> x.[i] |]


let ra = new System.Collections.Generic.List<int>( [1 .. 100] )

ra.[3..4]

Kind regards

don

By on 5/19/2009 1:50 AM ()

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