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Nested Recursive Loop

Nested recursive loop which has certain uses cases for loop optimization when you don't want to traverse across entire ranges but rather subsets incrementally and decrementally etc.

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open System

// Regular nested loop
let mutable sum = 0

for i in 1 .. 10 do
    for j in 1 .. 10 do
        for k in 1 .. 10 do
            sum <- sum + 1

printfn "%A" sum

// Nested recursive loop equivalent
let rec loop1 c sum = 
    if c >= 10 then
        sum
    else
        loop1 (c + 1) (sum + 1)

let rec loop2 c sum = 
    if c >= 9 then
        sum
    else
        loop2 (c + 1) (loop1 0 (sum + 1))

let rec loop3 c sum = 
    if c >= 10 then
        sum
    else
        loop3 (c + 1) (loop2 0 (sum + 1))

loop3 0 0
namespace System
val mutable sum : int
val i : int32
val j : int32
val k : int32
val printfn : format:Printf.TextWriterFormat<'T> -> 'T
val loop1 : c:int -> sum:int -> int
val c : int
val sum : int
val loop2 : c:int -> sum:int -> int
val loop3 : c:int -> sum:int -> int
Raw view Test code New version

More information

Link:http://fssnip.net/80A
Posted:3 years ago
Author:Martin Lockstrom
Tags: #nested loops , #recursion

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