{
open Grammar

exception IllegalCharacter of char
}

let whitespace = [' ' '\t' '\r' '\n']+
let letter = ['a'-'z' 'A'-'Z']
let ident = letter+

rule token =
  parse
  | whitespace { token lexbuf }

  | "(" { LPR }
  | ")" { RPR }
  | "[" { LBR }
  | "]" { RBR }
  | "->" { ARROW }
  | ":=" { ASSIGN }
  | "*" { ASTERISK }
  | "\\" { BACKSLASH }
  | "::" { DOUBLE_COLON }
  | ":" { COLON }
  | "," { COMMA }
  | "." { DOT }
  | "=>" { FATARROW }
  | "_" { UNDERSCORE }

  | "def" { DEF }

  | "fst" { FST }
  | "snd" { SND }

  | "type" { TYPE }

  | "bool" { BOOL }
  | "true" { TRUE }
  | "false" { FALSE }
  | "bool-elim" { BOOL_ELIM }
  | "at" { AT }

  | ident { IDENT (Lexing.lexeme lexbuf) }

  | eof { EOF }
  | (_ as illegal_char) { raise (IllegalCharacter illegal_char) }