{
  open Parser
}

let space = [' ' '\t' '\r']
let digit = ['0'-'9']
let lower = ['a' - 'z']
let upper = ['A' -'Z']
let alpha = lower | upper

rule token = parse
  | space+  { token lexbuf }
  | "("     { LPAREN }
  | ")"     { RPAREN }
  | "<"     { LANGLE }
  | ">"     { RANGLE }
  | "int"   { INT }
  | "fun"   { FUN }
  | "shift" { SHIFT }
  | "->"    { ARROW }
  | "=>"    { DARROW }
  | "|-"    { DARROW }
  | ":"     { COLON }
  | ","     { COMMA }
  | "/"     { SLASH }
  | ";;"    { EOI }
  | upper(alpha|digit)*
            { LVAR (Lexing.lexeme lexbuf) } 
  | alpha(alpha|digit)*
            { VAR (Lexing.lexeme lexbuf) }
  | _       { failwith ("unknown token" ^ Lexing.lexeme lexbuf) }