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Skip that is safe when not enough lines

A version of Seq.skip which doesn't throw an exception if there are fewer lines in the sequence than you have asked to skip.

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module Seq =

    /// Skip the first n lines of the sequence, and don't throw an exception if there are fewer than n lines.
    let skipIf n s =
        s
        |> Seq.mapi (fun i elem -> i, elem)
        |> Seq.choose (fun (i, elem) -> if i >= n then Some(elem) else None)

module Examples = 

    let skipdemo01 =
        Seq.init 0 (fun x -> x)
        |> Seq.skipIf 1

    let skipdemo11 =
        Seq.init 1 (fun x -> x)
        |> Seq.skipIf 1

    let skipdemo02 =
        Seq.init 0 (fun x -> x)
        |> Seq.skipIf 2

    let skipdemo32 =
        Seq.init 3 (fun x -> x)
        |> Seq.skipIf 2

    let skipdemo30 =
        Seq.init 3 (fun x -> x)
        |> Seq.skipIf 0

module Seq

from Microsoft.FSharp.Collections

val skipIf : n:int -> s:seq<'a> -> seq<'a>

Full name: Script.Seq.skipIf

Skip the first n lines of the sequence, and don't throw an exception if there are fewer than n lines.

val n : int

val s : seq<'a>

val mapi : mapping:(int -> 'T -> 'U) -> source:seq<'T> -> seq<'U>

Full name: Microsoft.FSharp.Collections.Seq.mapi

val i : int

val elem : 'a

val choose : chooser:('T -> 'U option) -> source:seq<'T> -> seq<'U>

Full name: Microsoft.FSharp.Collections.Seq.choose

union case Option.Some: Value: 'T -> Option<'T>

union case Option.None: Option<'T>

module Examples

from Script

val skipdemo01 : seq<int>

Full name: Script.Examples.skipdemo01

Multiple items
module Seq

from Script

--------------------
module Seq

from Microsoft.FSharp.Collections

val init : count:int -> initializer:(int -> 'T) -> seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.init

val x : int

val skipdemo11 : seq<int>

Full name: Script.Examples.skipdemo11

val skipdemo02 : seq<int>

Full name: Script.Examples.skipdemo02

val skipdemo32 : seq<int>

Full name: Script.Examples.skipdemo32

val skipdemo30 : seq<int>

Full name: Script.Examples.skipdemo30

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More information

Link:	http://fssnip.net/cH
Posted:	12 years ago
Author:	Kit Eason
Tags:	sequences skip