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Project Euler #1

This snippet is code that solves first Project Euler problem. It finds the sum of all the multiples of 3 or 5 below 1000. Please add other (more efficient, succinct or interesting) solutions to this snippet.

Using declared functions

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let range = [0..999]
let condition x = x % 3 = 0 || x % 5 = 0

range 
  |> List.filter condition 
  |> List.fold (+) 0

Using lambda functions

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[0..999] 
  |> Seq.filter (fun x -> x % 3 = 0 || x % 5 = 0) 
  |> Seq.reduce (+)

Using sequence expressions

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seq { for x in 0 .. 999 do
      if x % 3 = 0 || x % 5 = 0 then yield x }
|> Seq.sum

Using pattern match for ultimate speed

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let rec multiple x =
  match x with
  | _ when x = 1000 -> 0
  | _ when x%3 = 0 || x%5 = 0 -> x + multiple (x+1)
  | _ -> multiple (x+1)
  
multiple 1

val range : int list

Full name: Script.range

val condition : x:int -> bool

Full name: Script.condition

val x : int

Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

Full name: Microsoft.FSharp.Collections.List<_>

val filter : predicate:('T -> bool) -> list:'T list -> 'T list

Full name: Microsoft.FSharp.Collections.List.filter

val fold : folder:('State -> 'T -> 'State) -> state:'State -> list:'T list -> 'State

Full name: Microsoft.FSharp.Collections.List.fold

module Seq

from Microsoft.FSharp.Collections

val filter : predicate:('T -> bool) -> source:seq<'T> -> seq<'T>

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

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

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

Multiple items
val seq : sequence:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Core.Operators.seq

--------------------
type seq<'T> = System.Collections.Generic.IEnumerable<'T>

Full name: Microsoft.FSharp.Collections.seq<_>

val sum : source:seq<'T> -> 'T (requires member ( + ) and member get_Zero)

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

val multiple : x:int -> int

Full name: Script.multiple

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More information

Link:	http://fssnip.net/1a
Posted:	5 years ago
Author:	Eugene Gavrin
Tags:	list , filter , fold , euler problem , inclusion-exclusion