Comments on: Run-Length Encoding in F# http://www.claudiocherubino.it/2008/03/07/run-length-encoding-in-f/?utm_source=rss&utm_medium=rss&utm_campaign=run-length-encoding-in-f Life of a Googler Sat, 04 Sep 2010 11:07:11 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: Decoding RLE in F# » FSharp.it http://www.claudiocherubino.it/2008/03/07/run-length-encoding-in-f/comment-page-1/#comment-20423 Decoding RLE in F# » FSharp.it Tue, 11 Mar 2008 11:25:59 +0000 http://www.claudiocherubino.it/2008/03/07/run-length-encoding-in-f/#comment-20423 [...] A couple of days ago, we saw how to implement the Run-Length Encoding (RLE) algorithm to encode an array of elements and now we are going to describe how to restore the original array. [...] [...] A couple of days ago, we saw how to implement the Run-Length Encoding (RLE) algorithm to encode an array of elements and now we are going to describe how to restore the original array. [...]

]]> By: Michiel Borkent http://www.claudiocherubino.it/2008/03/07/run-length-encoding-in-f/comment-page-1/#comment-20424 Michiel Borkent Sat, 08 Mar 2008 11:41:06 +0000 http://www.claudiocherubino.it/2008/03/07/run-length-encoding-in-f/#comment-20424 Here is my version of run which builds the encoding directly during the recursion: [fsharp] #light let source = ['a'; 'a'; 'a'; 'a'; 'b'; 'c'; 'c'; 'a'; 'a'; 'd'; 'e'; 'e'; 'e'; 'e'] let encode list = let rec altpack list pack = match (list,pack) with | ([],_) -> (list,List.rev pack) | (hl::tl,[]) -> altpack tl [(1,hl)] | (hl::tl,(x,y)::tp) -> if y=hl then altpack tl ((x+1,y)::tp) else altpack tl ((1,hl)::pack) snd (altpack list []) let answer = encode source [/fsharp] Here is my version of run which builds the encoding directly during the recursion:

#light

let source = ['a'; 'a'; 'a'; 'a'; 'b'; 'c'; 'c'; 'a'; 'a'; 'd'; 'e'; 'e'; 'e'; 'e']

let encode list =
    let rec altpack list pack =
        match (list,pack) with
        | ([],_) -> (list,List.rev pack)
        | (hl::tl,[]) -> altpack tl [(1,hl)]
        | (hl::tl,(x,y)::tp) -> if y=hl then altpack tl ((x+1,y)::tp)
                                              else altpack tl ((1,hl)::pack)
    snd (altpack list [])

let answer = encode source
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