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FizzBuzz with Forward Composition

This version of FizzBuzz uses forward composition instead of recursive pattern matching (see http://fssnip.net/e7). All the rules, including the default case, are in a list of lambdas that can be easily modified. The function executeRules composes the list into a single rule and executes it.

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let fizzRules = 
    [
        (fun i s -> if i % 3 = 0 then s + "Fizz" else s)
        (fun i s -> if i % 5 = 0 then s + "Buzz" else s)
        (fun i s -> if i % 7 = 0 then s + "Bazz" else s)
        (fun i s -> if i % 11 = 0 then s + "Bop" else s)
        (fun i s -> if s = "" then i.ToString() else s)
    ]

let executeRules rules accum i =
    let allRules =
        rules
            |> Seq.map (fun f -> f i)
            |> Seq.reduce ((fun x -> x) (>>))
    allRules accum

let fizzBuzz = executeRules fizzRules ""

[ 1 .. 105 ]
    |> Seq.map fizzBuzz
    |> Seq.iter (printfn "%s")

val fizzRules : (int -> string -> string) list

Full name: Script.fizzRules

val i : int

val s : string

System.Int32.ToString() : string
System.Int32.ToString(provider: System.IFormatProvider) : string
System.Int32.ToString(format: string) : string
System.Int32.ToString(format: string, provider: System.IFormatProvider) : string

val executeRules : rules:seq<('a -> 'b -> 'b)> -> accum:'b -> i:'a -> 'b

Full name: Script.executeRules

val rules : seq<('a -> 'b -> 'b)>

val accum : 'b

val i : 'a

val allRules : ('b -> 'b)

module Seq

from Microsoft.FSharp.Collections

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

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

val f : ('a -> 'b -> 'b)

val reduce : reduction:('T -> 'T -> 'T) -> source:seq<'T> -> 'T

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

val x : (('b -> 'b) -> ('b -> 'b) -> 'b -> 'b)

val fizzBuzz : (int -> string)

Full name: Script.fizzBuzz

val iter : action:('T -> unit) -> source:seq<'T> -> unit

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

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

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More information

Link:	http://fssnip.net/e8
Posted:	12 years ago
Author:	Richard Broida
Tags:	fizzbuzz , kata , rules , function composition , lambdas