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# Soundex phonetic algorithm

Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English implemented in F#. https://en.wikipedia.org/wiki/Soundex

 ``` 1: 2: 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: 13: 14: 15: 16: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: 31: 32: 33: 34: 35: 36: 37: 38: 39: 40: 41: 42: 43: 44: 45: 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58: 59: 60: 61: 62: 63: 64: 65: 66: 67: 68: 69: 70: 71: 72: 73: 74: 75: 76: 77: ``` ``````let americanSoundex (x : string) = let toString (xs : char list) = new System.String(xs |> Array.ofList) let _americanSoundex = let toUpper (x : string) = x.ToUpper() let toArray (x : string) = x.ToCharArray() let f1 ch = match ch with | 'H' | 'W' -> false | _ -> true let f2 ch = match ch with | 'B' | 'F' | 'P' | 'V' -> '1' | 'C' | 'G' | 'J' | 'K' | 'Q' | 'S' | 'X' | 'Z' -> '2' | 'D' | 'T' -> '3' | 'L' -> '4' | 'M' | 'N' -> '5' | 'R' -> '6' | _ -> ch let rec f3 xs = match xs with | h0 :: h1 :: t -> h0 :: f3 (if (h0 = h1) then t else (h1 :: t)) | h :: _ -> [h] | _ -> [] let f4 ch = match ch with | 'A' | 'E' | 'I' | 'O' | 'U' | 'Y' -> false | _ -> true let f5 ch first = if ('0' <= ch && ch <= '9') then first else ch let f6 xs = let len = List.length xs seq{for i = 0 to 3 - len do yield '0'} |> Seq.append (xs |> Seq.take (System.Math.Min(4, len))) |> Seq.toList let a = x |> toUpper |> toArray |> Array.toList let b = a |> List.filter f1 //1 let c = b |> List.map f2 //2 let d = c |> f3 //3 let e = d |> List.tail |> List.filter f4 //4 let f = f5 (d |> List.head) (a |> List.head) :: e //5 f6 f //6 if (x.Length > 0) then toString(_americanSoundex) else "0000" ["Robert"; "Rupert"; "Robbert"; "Rubin"; "Beer"; "Bear"; "Bearer"; "Smith"; "Smyth"; "Ashcraft"; "Ashcroft"; "Tymczak"; "Pfister"] |> List.map (fun x -> (x, americanSoundex x)) |> List.iter (fun (x, y) -> printfn "%-8s = %s" x y) (* Robert = R163 Rupert = R163 Robbert = R163 Rubin = R150 Beer = B600 Bear = B600 Bearer = B660 Smith = S530 Smyth = S530 Ashcraft = A261 Ashcroft = A261 Tymczak = T522 Pfister = P236 *) ``````
val americanSoundex : x:string -> System.String

Full name: Script.americanSoundex
val x : string
Multiple items
val string : value:'T -> string

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

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string
val toString : (char list -> System.String)
val xs : char list
Multiple items
val char : value:'T -> char (requires member op_Explicit)

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

--------------------
type char = System.Char

Full name: Microsoft.FSharp.Core.char
type 'T list = List<'T>

Full name: Microsoft.FSharp.Collections.list<_>
namespace System
Multiple items
type String =
new : value:char -> string + 7 overloads
member Chars : int -> char
member Clone : unit -> obj
member CompareTo : value:obj -> int + 1 overload
member Contains : value:string -> bool
member CopyTo : sourceIndex:int * destination:char[] * destinationIndex:int * count:int -> unit
member EndsWith : value:string -> bool + 2 overloads
member Equals : obj:obj -> bool + 2 overloads
member GetEnumerator : unit -> CharEnumerator
member GetHashCode : unit -> int
...

Full name: System.String

--------------------
System.String(value: nativeptr<char>) : unit
System.String(value: nativeptr<sbyte>) : unit
System.String(value: char []) : unit
System.String(c: char, count: int) : unit
System.String(value: nativeptr<char>, startIndex: int, length: int) : unit
System.String(value: nativeptr<sbyte>, startIndex: int, length: int) : unit
System.String(value: char [], startIndex: int, length: int) : unit
System.String(value: nativeptr<sbyte>, startIndex: int, length: int, enc: System.Text.Encoding) : unit
module Array

from Microsoft.FSharp.Collections
val ofList : list:'T list -> 'T []

Full name: Microsoft.FSharp.Collections.Array.ofList
val toUpper : (string -> string)
System.String.ToUpper() : string
System.String.ToUpper(culture: System.Globalization.CultureInfo) : string
val toArray : (string -> char [])
System.String.ToCharArray() : char []
System.String.ToCharArray(startIndex: int, length: int) : char []
val f1 : (char -> bool)
val ch : char
val f2 : (char -> char)
val f3 : ('a list -> 'a list) (requires equality)
val xs : 'a list (requires equality)
val h0 : 'a (requires equality)
val h1 : 'a (requires equality)
val t : 'a list (requires equality)
val h : 'a (requires equality)
val f4 : (char -> bool)
val f5 : (char -> char -> char)
val first : char
val f6 : (char list -> char list)
val len : int
Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
| ( [] )
| ( :: ) of Head: 'T * Tail: 'T list
interface IEnumerable
interface IEnumerable<'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 length : list:'T list -> int

Full name: Microsoft.FSharp.Collections.List.length
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 i : int
module Seq

from Microsoft.FSharp.Collections
val append : source1:seq<'T> -> source2:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.append
val take : count:int -> source:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.take
type Math =
static val PI : float
static val E : float
static member Abs : value:sbyte -> sbyte + 6 overloads
static member Acos : d:float -> float
static member Asin : d:float -> float
static member Atan : d:float -> float
static member Atan2 : y:float * x:float -> float
static member BigMul : a:int * b:int -> int64
static member Ceiling : d:decimal -> decimal + 1 overload
static member Cos : d:float -> float
...

Full name: System.Math
System.Math.Min(val1: decimal, val2: decimal) : decimal
System.Math.Min(val1: float, val2: float) : float
System.Math.Min(val1: float32, val2: float32) : float32
System.Math.Min(val1: uint64, val2: uint64) : uint64
System.Math.Min(val1: int64, val2: int64) : int64
System.Math.Min(val1: uint32, val2: uint32) : uint32
System.Math.Min(val1: int, val2: int) : int
System.Math.Min(val1: uint16, val2: uint16) : uint16
System.Math.Min(val1: int16, val2: int16) : int16
System.Math.Min(val1: byte, val2: byte) : byte
val toList : source:seq<'T> -> 'T list

Full name: Microsoft.FSharp.Collections.Seq.toList
val a : char list
val toList : array:'T [] -> 'T list

Full name: Microsoft.FSharp.Collections.Array.toList
val b : char list
val filter : predicate:('T -> bool) -> list:'T list -> 'T list

Full name: Microsoft.FSharp.Collections.List.filter
val c : char list
val map : mapping:('T -> 'U) -> list:'T list -> 'U list

Full name: Microsoft.FSharp.Collections.List.map
val d : char list
val e : char list
val tail : list:'T list -> 'T list

Full name: Microsoft.FSharp.Collections.List.tail
val f : char list
val head : list:'T list -> 'T