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annotate examples/OCaml-Kaleidoscope/Chapter3/parser.ml @ 0:95c75e76d11b LLVM3.4

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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1 (*===---------------------------------------------------------------------===
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2 * Parser
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3 *===---------------------------------------------------------------------===*)
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4
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5 (* binop_precedence - This holds the precedence for each binary operator that is
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6 * defined *)
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7 let binop_precedence:(char, int) Hashtbl.t = Hashtbl.create 10
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8
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9 (* precedence - Get the precedence of the pending binary operator token. *)
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10 let precedence c = try Hashtbl.find binop_precedence c with Not_found -> -1
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11
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12 (* primary
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13 * ::= identifier
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14 * ::= numberexpr
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15 * ::= parenexpr *)
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16 let rec parse_primary = parser
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17 (* numberexpr ::= number *)
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18 | [< 'Token.Number n >] -> Ast.Number n
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19
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20 (* parenexpr ::= '(' expression ')' *)
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21 | [< 'Token.Kwd '('; e=parse_expr; 'Token.Kwd ')' ?? "expected ')'" >] -> e
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22
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23 (* identifierexpr
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24 * ::= identifier
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25 * ::= identifier '(' argumentexpr ')' *)
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26 | [< 'Token.Ident id; stream >] ->
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27 let rec parse_args accumulator = parser
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28 | [< e=parse_expr; stream >] ->
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29 begin parser
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30 | [< 'Token.Kwd ','; e=parse_args (e :: accumulator) >] -> e
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31 | [< >] -> e :: accumulator
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32 end stream
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33 | [< >] -> accumulator
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34 in
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35 let rec parse_ident id = parser
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36 (* Call. *)
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37 | [< 'Token.Kwd '(';
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38 args=parse_args [];
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39 'Token.Kwd ')' ?? "expected ')'">] ->
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40 Ast.Call (id, Array.of_list (List.rev args))
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41
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42 (* Simple variable ref. *)
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43 | [< >] -> Ast.Variable id
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44 in
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45 parse_ident id stream
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46
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47 | [< >] -> raise (Stream.Error "unknown token when expecting an expression.")
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48
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49 (* binoprhs
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50 * ::= ('+' primary)* *)
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51 and parse_bin_rhs expr_prec lhs stream =
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52 match Stream.peek stream with
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53 (* If this is a binop, find its precedence. *)
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54 | Some (Token.Kwd c) when Hashtbl.mem binop_precedence c ->
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55 let token_prec = precedence c in
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56
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57 (* If this is a binop that binds at least as tightly as the current binop,
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58 * consume it, otherwise we are done. *)
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59 if token_prec < expr_prec then lhs else begin
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60 (* Eat the binop. *)
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61 Stream.junk stream;
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62
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63 (* Parse the primary expression after the binary operator. *)
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64 let rhs = parse_primary stream in
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65
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66 (* Okay, we know this is a binop. *)
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67 let rhs =
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68 match Stream.peek stream with
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69 | Some (Token.Kwd c2) ->
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70 (* If BinOp binds less tightly with rhs than the operator after
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71 * rhs, let the pending operator take rhs as its lhs. *)
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72 let next_prec = precedence c2 in
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73 if token_prec < next_prec
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74 then parse_bin_rhs (token_prec + 1) rhs stream
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75 else rhs
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76 | _ -> rhs
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77 in
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78
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79 (* Merge lhs/rhs. *)
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80 let lhs = Ast.Binary (c, lhs, rhs) in
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81 parse_bin_rhs expr_prec lhs stream
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82 end
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83 | _ -> lhs
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84
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85 (* expression
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86 * ::= primary binoprhs *)
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87 and parse_expr = parser
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88 | [< lhs=parse_primary; stream >] -> parse_bin_rhs 0 lhs stream
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89
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90 (* prototype
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91 * ::= id '(' id* ')' *)
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92 let parse_prototype =
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93 let rec parse_args accumulator = parser
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94 | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
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95 | [< >] -> accumulator
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96 in
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97
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98 parser
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99 | [< 'Token.Ident id;
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100 'Token.Kwd '(' ?? "expected '(' in prototype";
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101 args=parse_args [];
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102 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
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103 (* success. *)
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104 Ast.Prototype (id, Array.of_list (List.rev args))
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105
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106 | [< >] ->
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107 raise (Stream.Error "expected function name in prototype")
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108
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109 (* definition ::= 'def' prototype expression *)
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110 let parse_definition = parser
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111 | [< 'Token.Def; p=parse_prototype; e=parse_expr >] ->
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112 Ast.Function (p, e)
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113
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114 (* toplevelexpr ::= expression *)
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115 let parse_toplevel = parser
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116 | [< e=parse_expr >] ->
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117 (* Make an anonymous proto. *)
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118 Ast.Function (Ast.Prototype ("", [||]), e)
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119
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120 (* external ::= 'extern' prototype *)
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121 let parse_extern = parser
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122 | [< 'Token.Extern; e=parse_prototype >] -> e