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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 recursive function for ultimate speed

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let rec multiple x =
  if x = 1000 then 0
  elif x%3 = 0 || x%5 = 0 then x + multiple (x+1)
  else multiple (x+1)
  
multiple 1

Using accumulator for tail-recursive and pattern matching

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let rec mul' acc x =
  match x with
  | 999L -> acc + x 
  | x when (x%3L=0L||x%5L=0L) ->       
      mul' (acc + x) (x + 1L)   
  | _ -> 
      mul' acc (x + 1L)

mul' 0L 1L
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
val mul' : acc:int64 -> x:int64 -> int64

Full name: Script.mul'
val acc : int64
val x : int64

More information

Link:http://fssnip.net/1a
Posted:6 years ago
Author:Eugene Gavrin
Tags: list , filter , fold , euler problem