InteractivePerformance.fsx

// Start in VS: View -> Other Windows -> F# Interactive

open System

// Turn on timing in F# interactive
#time

// Performance bottle kneck
let formatKey (a:string,b:string) = 
   String.Format("{0}:{1}", a, b)

// Time it
for i = 1 to 1000000 do ignore(formatKey("aaa","bbb"))

// 5x faster version
let concatKey (a:string,b:string) = 
    String.Concat(a,":",b)

// Time it
for i = 1 to 1000000 do ignore(concatKey("aaa","bbb"))


open System.Collections.Generic

// Inserting at end of .Net List
let xs = List<int>()
for i = 1 to 1000000 do xs.Add(i)

// Inserting at start of .Net list
xs.Clear()
for i = 1 to 1000000 do xs.Insert(0,i)
// Wait 5 minutes...
// Or right click & Reset Interactive Session