open System

open System.Text

open Microsoft.FSharp.Core.LanguagePrimitives.IntrinsicOperators

open Microsoft.FSharp.Core.Operators

open Microsoft.FSharp.Core.Operators.Checked

open Microsoft.FSharp.Collections

[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]

[<RequireQualifiedAccess>]

module String =

let inline emptyIfNull str =

match str with

| null -> String.Empty

| _ -> str

[<CompiledName("Concat")>]

let concat sep (strings : seq<string>) =

String.Join(sep, Seq.toArray strings)

[<CompiledName("Iterate")>]

let iter (f : (char -> unit)) (str:string) =

let str = emptyIfNull str

for i = 0 to str.Length - 1 do

f str.[i]

[<CompiledName("IterateIndexed")>]

let iteri f (str:string) =

let str = emptyIfNull str

let f = OptimizedClosures.FSharpFunc<_,_,_>.Adapt(f)

for i = 0 to str.Length - 1 do

f.Invoke(i, str.[i])

[<CompiledName("Map")>]

let map (f: char -> char) (str:string) =

let str = emptyIfNull str

let res = StringBuilder str.Length

str |> iter (fun c -> res.Append(f c) |> ignore)

res.ToString()

[<CompiledName("MapIndexed")>]

let mapi (f: int -> char -> char) (str:string) =

let str = emptyIfNull str

let res = StringBuilder str.Length

let f = OptimizedClosures.FSharpFunc<_,_,_>.Adapt(f)

str |> iteri (fun i c -> res.Append(f.Invoke(i, c)) |> ignore)

res.ToString()

[<CompiledName("Filter")>]

let filter (f: char -> bool) (str:string) =

let str = emptyIfNull str

let res = StringBuilder str.Length

str |> iter (fun c -> if f c then res.Append c |> ignore)

res.ToString()

[<CompiledName("Collect")>]

let collect (f: char -> string) (str:string) =

let str = emptyIfNull str

let res = StringBuilder str.Length

str |> iter (fun c -> res.Append(f c) |> ignore)

res.ToString()

[<CompiledName("Initialize")>]

let init (count:int) (initializer: int-> string) =

if count < 0 then invalidArgInputMustBeNonNegative "count" count

let res = StringBuilder count

for i = 0 to count - 1 do

res.Append(initializer i) |> ignore

res.ToString()

[<CompiledName("Replicate")>]

let replicate (count:int) (str:string) =

if count < 0 then invalidArgInputMustBeNonNegative "count" count

let str = emptyIfNull str

let res = StringBuilder str.Length

for i = 0 to count - 1 do

res.Append str |> ignore

res.ToString()

[<CompiledName("ForAll")>]

let forall f (str:string) =

let str = emptyIfNull str

let rec check i = (i >= str.Length) || (f str.[i] && check (i+1))

check 0

[<CompiledName("Exists")>]

let exists f (str:string) =

let str = emptyIfNull str

let rec check i = (i < str.Length) && (f str.[i] || check (i+1))

check 0

[<CompiledName("Length")>]

let length (str:string) =

let str = emptyIfNull str

str.Length