fancy-parser.mly 11 KB
Newer Older
1 2 3
/* This is the fancy version of the parser, to be processed by menhir.
   It is kept in sync with [Parser], but exercises menhir's features. */

4 5 6 7
/* As of 2014/12/02, the $previouserror keyword and the --error-recovery
   mode no longer exists. Thus, we replace all calls to [Error.signal]
   with calls to [Error.error], and report just one error. */

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
/* ------------------------------------------------------------------------- */
/* Imports. */

%{

open ConcreteSyntax
open Syntax
open Positions

%}

/* ------------------------------------------------------------------------- */
/* Tokens. */

%token TOKEN TYPE LEFT RIGHT NONASSOC START PREC PUBLIC COLON BAR EOF EQUAL
%token INLINE LPAREN RPAREN COMMA QUESTION STAR PLUS PARAMETER
%token <string Positions.located> LID UID 
%token <Stretch.t> HEADER
%token <Stretch.ocamltype> OCAMLTYPE
27
%token <Stretch.t Lazy.t> PERCENTPERCENT
28
%token <Syntax.identifier option array -> Action.t> ACTION
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

/* ------------------------------------------------------------------------- */
/* Start symbol. */

%start <ConcreteSyntax.grammar> grammar

/* ------------------------------------------------------------------------- */
/* Priorities. */

/* These declarations solve a shift-reduce conflict in favor of
   shifting: when the declaration of a non-terminal symbol begins with
   a leading bar, it is understood as an (insignificant) leading
   optional bar, *not* as an empty right-hand side followed by a bar.
   This ambiguity arises due to the existence of a new notation for
   letting several productions share a single semantic action. */

%nonassoc no_optional_bar
%nonassoc BAR

%%

/* ------------------------------------------------------------------------- */
/* A grammar consists of declarations and rules, followed by an optional
   trailer, which we do not parse. */

grammar:
  ds = declaration* PERCENTPERCENT rs = rule* t = trailer
    { 
      { 
	pg_filename          = ""; (* filled in by the caller *)
	pg_declarations      = List.flatten ds;
60
	pg_rules	     = rs @ ParserAux.rules();
61 62 63 64 65 66 67 68 69 70 71 72 73
	pg_trailer           = t
      }
    }

/* ------------------------------------------------------------------------- */
/* A declaration is an %{ Objective Caml header %}, or a %token, %start,
   %type, %left, %right, or %nonassoc declaration. */

declaration:

| h = HEADER /* lexically delimited by %{ ... %} */
    { [ with_poss $startpos $endpos (DCode h) ] }

74
| TOKEN t = OCAMLTYPE? ts = clist(terminal)
75 76
    { List.map (Positions.map (fun terminal -> DToken (t, terminal))) ts }

77
| START t = OCAMLTYPE? nts = clist(nonterminal)
78 79 80 81 82 83 84 85 86 87
    /* %start <ocamltype> foo is syntactic sugar for %start foo %type <ocamltype> foo */
    {
      match t with
      | None ->
	  List.map (Positions.map (fun nonterminal -> DStart nonterminal)) nts
      | Some t ->
	  Misc.mapd (fun ntloc ->
            Positions.mapd (fun nt -> DStart nt, DType (t, ParameterVar ntloc)) ntloc) nts
    }

88
| TYPE t = OCAMLTYPE ss = clist(strict_actual)
89 90 91
    { List.map (Positions.map (fun nt -> DType (t, nt)))
        (List.map Parameters.with_pos ss) }

92
| k = priority_keyword ss = clist(symbol)
93
    { let prec = ParserAux.new_precedence_level $startpos(k) $endpos(k) in
94 95 96 97 98
      List.map (Positions.map (fun symbol -> DTokenProperties (symbol, k, prec))) ss }

| PARAMETER t = OCAMLTYPE
    { [ with_poss $startpos $endpos (DParameter t) ] }

99 100 101 102 103 104 105 106 107 108 109
/* This production recognizes tokens that are valid in the rules section,
   but not in the declarations section. This is a hint that a %% was
   forgotten. */

| rule_specific_token
    {
      Error.error (Positions.two $startpos $endpos)
        "syntax error inside a declaration.\n\
         Did you perhaps forget the %% that separates declarations and rules?"
    }

110 111 112 113 114 115 116 117
priority_keyword:
  LEFT
    { LeftAssoc }
| RIGHT
    { RightAssoc }
| NONASSOC
    { NonAssoc }

118 119 120 121 122 123 124
%inline rule_specific_token:
| PUBLIC
| INLINE
| COLON
| EOF
    { () }

125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166
/* ------------------------------------------------------------------------- */
/* Our lists of symbols are separated with optional commas. Order is
   irrelevant. */

%inline clist(X):
  xs = separated_nonempty_list(COMMA?, X)
    { xs }

/* ------------------------------------------------------------------------- */
/* A symbol is a terminal or nonterminal symbol. One would like to
   require nonterminal symbols to begin with a lowercase letter, so as
   to lexically distinguish them from terminal symbols, which must
   begin with an uppercase letter. However, for compatibility with
   ocamlyacc, this is impossible. It can be required only for
   nonterminal symbols that are also start symbols. */

symbol:
  id = LID
| id = UID
    { id }

/* ------------------------------------------------------------------------- */
/* Terminals must begin with an uppercase letter. Nonterminals that are
   declared to be start symbols must begin with a lowercase letter. */

%inline terminal:
  id = UID
    { id }

%inline nonterminal:
  id = LID
    { id }

/* ------------------------------------------------------------------------- */
/* A rule defines a symbol. It is optionally declared %public, and optionally
   carries a number of formal parameters. The right-hand side of the definition
   consists of a list of productions. */

rule:
  flags = flags                                             /* flags */
  symbol = symbol                                           /* the symbol that is being defined */
  params = plist(symbol)                                    /* formal parameters */
167
  COLON
168
  optional_bar
169
  branches = branches
170 171
    { 
      let public, inline = flags in
172 173 174 175 176 177 178 179
      {
        pr_public_flag = public; 
        pr_inline_flag = inline; 
        pr_nt          = Positions.value symbol;
        pr_positions   = [ Positions.position symbol ];
        pr_parameters  = List.map Positions.value params;
        pr_branches    = branches
      }
180 181
    }

182
%inline branches:
183
  prods = separated_nonempty_list(BAR, production_group)
184 185
    { List.flatten prods }

186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208
flags:
  /* epsilon */
    { false, false }
| PUBLIC
    { true, false }
| INLINE
    { false, true }
| PUBLIC INLINE
| INLINE PUBLIC
    { true, true }

optional_bar:
  /* epsilon */ %prec no_optional_bar
| BAR
    { () }

/* ------------------------------------------------------------------------- */
/* A production group consists of a list of productions, followed by a
   semantic action and an optional precedence specification. */

production_group:
  productions = separated_nonempty_list(BAR, production)
  action = ACTION
209
  oprec2 = ioption(precedence)
210
    {
211 212 213 214
      (* If multiple productions share a single semantic action, check
         that all of them bind the same names. *)
      ParserAux.check_production_group productions;
      (* Then, *)
215
      List.map (fun (producers, oprec1, level, pos) ->
216 217 218 219
        (* Replace [$i] with [_i]. *)
        let pr_producers = ParserAux.normalize_producers producers in
        (* Distribute the semantic action. Also, check that every [$i]
           is within bounds. *)
220
        let action : Syntax.identifier option array -> Action.t = action in
221
        let pr_action = action (ParserAux.producer_names producers) in
222
	{
223 224
	  pr_producers;
	  pr_action;
225
	  pr_branch_prec_annotation   = ParserAux.override pos oprec1 oprec2;
226
	  pr_branch_production_level  = level;
227 228
	  pr_branch_position          = pos
	})
229
      productions
230 231 232 233 234 235 236 237 238 239 240
    }

%inline precedence:
  PREC symbol = symbol
    { symbol }

/* ------------------------------------------------------------------------- */
/* A production is a list of producers, optionally followed by a
   precedence declaration. */

production:
241
  producers = producer* oprec = ioption(precedence)
242 243
    { producers,
      oprec,
244
      ParserAux.new_production_level(),
245 246 247 248 249 250 251 252 253 254
      Positions.lex_join $startpos $endpos
    }

/* ------------------------------------------------------------------------- */
/* A producer is an actual parameter, possibly preceded by a
   binding.

   Because both [ioption] and [terminated] are defined as inlined by
   the standard library, this definition expands to two productions,
   one of which begins with id = LID, the other of which begins with
255
   p = actual. The token LID is in FIRST(actual),
256 257 258 259 260 261
   but the LR(1) formalism can deal with that. If [option] was used
   instead of [ioption], an LR(1) conflict would arise -- looking
   ahead at LID would not allow determining whether to reduce an
   empty [option] or to shift. */

producer:
262
| id = ioption(terminated(LID, EQUAL)) p = actual
263
    { position (with_poss $startpos $endpos ()), id, p }
264 265

/* ------------------------------------------------------------------------- */
266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289
/* The ideal syntax of actual parameters includes:
   1. a symbol, optionally applied to a list of actual parameters;
   2. an actual parameter followed with a modifier;
   3. an anonymous rule. (Not delimited by parentheses! Otherwise
      one would often end up writing two pairs of parentheses.) */

/* In order to avoid a few ambiguities, we restrict this ideal syntax as
   follows:
   a. Within a %type declaration, we use [strict_actual], which
      allows 1- and 2- (this is undocumented; the documentation says we
      require a symbol) but not 3-, which would not make semantic sense
      anyway.
   b. Within a producer, we use [actual], which allows 1- and
      2- but not 3-. Case 3- is allowed by switching to [lax_actual]
      within the actual arguments of an application, which are clearly
      delimited by parentheses and commas.
   c. In front of a modifier, we can never allow [lax_actual],
      as this would create an ambiguity: basically, [A | B?] could be
      interpreted either as [(A | B)?] or as [A | (B?)].
*/

%inline generic_actual(A, B):
(* 1- *)
  symbol = symbol actuals = plist(A)
290
    { Parameters.app symbol actuals }
291 292
(* 2- *)
| p = B m = modifier
293
    { ParameterApp (m, [ p ]) }
294

295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312
strict_actual:
  p = generic_actual(strict_actual, strict_actual)
    { p }

actual:
  p = generic_actual(lax_actual, actual)
    { p }

lax_actual:
  p = generic_actual(lax_actual, /* cannot be lax_ */ actual)
    { p }
(* 3- *)
| /* leading bar disallowed */
  branches = branches
    { let position = position (with_poss $startpos $endpos ()) in
      let symbol = ParserAux.anonymous position branches in
      ParameterVar (with_pos position symbol) }

313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343
/* ------------------------------------------------------------------------- */
/* Formal or actual parameter lists are delimited with parentheses and
   separated with commas. They are optional. */

%inline plist(X):
  params = loption(delimited(LPAREN, separated_nonempty_list(COMMA, X), RPAREN))
    { params }

/* ------------------------------------------------------------------------- */
/* The "?", "+", and "*" modifiers are short-hands for applications of
   certain parameterized nonterminals, defined in the standard library. */

modifier:
  QUESTION
    { with_poss $startpos $endpos "option" }
| PLUS
    { with_poss $startpos $endpos "nonempty_list" }
| STAR
    { with_poss $startpos $endpos "list" }

/* ------------------------------------------------------------------------- */
/* A trailer is announced by %%, but is optional. */

trailer:
  EOF
    { None }
| p = PERCENTPERCENT /* followed by actual trailer */
    { Some (Lazy.force p) }

%%