bundles/menhirLib/menhir-20120123/demos/calc-param/calc.ml

   1 (**************************************************************************)
   2 (*                                                                        *)
   3 (*  Menhir                                                                *)
   4 (*                                                                        *)
   5 (*  François Pottier, INRIA Rocquencourt                                  *)
   6 (*  Yann Régis-Gianas, PPS, Université Paris Diderot                      *)
   7 (*                                                                        *)
   8 (*  Copyright 2005-2008 Institut National de Recherche en Informatique    *)
   9 (*  et en Automatique. All rights reserved. This file is distributed      *)
  10 (*  under the terms of the Q Public License version 1.0, with the change  *)
  11 (*  described in file LICENSE.                                            *)
  12 (*                                                                        *)
  13 (**************************************************************************)
  14
  15 (* Let's do floating-point evaluation, for a change. *)
  16
  17 module FloatSemantics = struct
  18
  19   type number =
  20       float
  21
  22   let inject =
  23     float_of_int
  24
  25   let ( + ) = ( +. )
  26   let ( - ) = ( -. )
  27   let ( * ) = ( *. )
  28   let ( / ) = ( /. )
  29   let (~- ) = (~-. )
  30
  31 end
  32
  33 (* Let us now specialize our parameterized parser. *)
  34
  35 module FloatParser =
  36   Parser.Make(FloatSemantics)
  37
  38 (* The rest is as usual. *)
  39
  40 let () =
  41   let stdinbuf = Lexing.from_channel stdin in
  42   while true do
  43     (* Read line by line. *)
  44     let linebuf = Lexing.from_string (Lexer.line stdinbuf) in
  45     try
  46       (* Run the parser on a single line of input. *)
  47       Printf.printf "%.1f\n%!" (FloatParser.main Lexer.token linebuf)
  48     with
  49     | Lexer.Error msg ->
  50         Printf.fprintf stderr "%s%!" msg
  51     | FloatParser.Error ->
  52         Printf.fprintf stderr "At offset %d: syntax error.\n%!" (Lexing.lexeme_start linebuf)
  53   done