FParsec code to parse Advent of Code day 16 input to an Operation choice.

aoc2017-day16-parsers.fs

#r "packages/FParsec/lib/net40-client/FParsecCS.dll"
#r "packages/FParsec/lib/net40-client/FParsec.dll"
open FParsec

type Operation =
    | Spin of int
    | Exchange of int * int
    | Partner of char * char

type ParserState = unit

let pspin : Parser<Operation,ParserState> = 
    pchar 's' >>. pint32 |>> Spin
    
let pexchange = 
    pchar 'x' 
      >>. tuple2 (pint32 .>> pchar '/') pint32 
      |>> Exchange
      
let ppartner = 
    pchar 'p' 
      >>. tuple2 (asciiLetter .>> pchar '/') asciiLetter
      |>> Partner

let parseOperation = pspin <|> pexchange <|> ppartner

["po/k"; "x4/0"; "s12"] |> List.map (run parseOperation)
// Success: Partner ('o','k'); Success: Exchange (4,0); Success: Spin 12]