(* file: lexer.mll *)
(* Lexical analyzer returns one of the tokens:
   the token NUM of a floating point number,
   operators (PLUS, MINUS, MULTIPLY, DIVIDE, CARET, UMINUS),
   or NEWLINE.  It skips all blanks and tabs, unknown characters
   and raises End_of_file on EOF. *)
{
  open Rpcalc (* Assumes the parser file is "rpcalc.mly". *)
}
let digit = ['0'-'9']
rule token = parse
  | [' ' '\t']	{ token lexbuf }
  | '\n'	{ NEWLINE }
  | digit+
  | "." digit+
  | digit+ "." digit* as num
		{ NUM (float_of_string num) }
  | '+'		{ PLUS }
  | '-'		{ MINUS }
  | '*'		{ MULTIPLY }
  | '/'		{ DIVIDE }
  | '^'		{ CARET }
  | 'n'		{ UMINUS }
  | "if"	{ IF }
  | "then"	{ THEN }
  | "else"	{ ELSE }
  | '('		{ OPAREN }
  | ')'		{ CPAREN }
  | _		{ token lexbuf }
  | eof		{ raise End_of_file }