gaem/parser/lexer.d

   1 /* GML parser
   2  * coded by Ketmar // Invisible Vector <ketmar@ketmar.no-ip.org>
   3  * Understanding is not required. Only obedience.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 module gaem.parser.lexer is aliced;
  19
  20 import gaem.parser.tokens;
  21
  22
  23 // ////////////////////////////////////////////////////////////////////////// //
  24 public struct Loc {
  25   string file;
  26   int line, col;
  27   uint tpos;
  28
  29   string toString () const { import std.string : format; return "%s (%s,%s)".format(file, line, col); }
  30   string toStringNoFile () const { import std.string : format; return "(%s,%s)".format(line, col); }
  31
  32   @property bool valid () const pure nothrow @safe @nogc { pragma(inline, true); return (line > 0 && col > 0); }
  33 }
  34
  35
  36 // ////////////////////////////////////////////////////////////////////////// //
  37 public class ErrorAt : Exception {
  38   Loc loc;
  39
  40   this (string msg, Throwable next=null, string file=__FILE__, usize line=__LINE__) pure nothrow @safe @nogc { super(msg, file, line, next); }
  41   this (in Loc aloc, string msg, Throwable next=null, string file=__FILE__, usize line=__LINE__) pure nothrow @safe @nogc { loc = aloc; super(msg, file, line, next); }
  42 }
  43
  44
  45 // ////////////////////////////////////////////////////////////////////////// //
  46 public struct Token {
  47 public:
  48   enum Type {
  49     EOF = -1,
  50     Kw,
  51     Id,
  52     Str,
  53     Num,
  54     Spec,
  55   }
  56
  57 private:
  58   const(char)[] tkstr;
  59
  60 public:
  61   Loc loc, eloc; // token start, token end (after last char)
  62   Type type = Type.EOF; // token type
  63   union {
  64     Keyword kw;
  65     float num;
  66   }
  67
  68 @safe:
  69   void mustbeType (Token.Type tp, string msg="identifier expected", string file=__FILE__, usize line=__LINE__) {
  70     pragma(inline, true);
  71     if (type != tp) throw new ErrorAt(loc, msg, null, file, line);
  72   }
  73   void mustbeId (string msg="identifier expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); mustbeType(Type.Id, msg, file, line); }
  74   void mustbeStr (string msg="string expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); mustbeType(Type.Str, msg, file, line); }
  75   void mustbeNum (string msg="number expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); mustbeType(Type.Num, msg, file, line); }
  76
  77   string toString () const @trusted {
  78     import std.string : format;
  79     final switch (type) with (Type) {
  80       case EOF: return "(%s,%d): <EOF>".format(loc.line, loc.col);
  81       case Kw: return "(%s,%d): kw.%s <%s>".format(loc.line, loc.col, kw, tkstr);
  82       case Id: return "(%s,%d): Id:%s".format(loc.line, loc.col, tkstr);
  83       case Str: return "(%s,%d): Str:%s".format(loc.line, loc.col, Lexer.quote(tkstr));
  84       case Num: return "(%s,%d): Num:%s".format(loc.line, loc.col, num);
  85       case Spec: return "(%s,%d): Spec:<%s>".format(loc.line, loc.col, tkstr);
  86     }
  87     assert(0);
  88   }
  89
  90 nothrow:
  91   // get immutable string
  92   // this converts id to `string` via `.idup`, use with caution!
  93   // `.idup` is used to not anchor the whole source string
  94   @property string istr () { pragma(inline, true); return (tkstr.length ? tkstr.idup : null); }
  95
  96 const pure nothrow @nogc:
  97   bool opEquals (Keyword akw) { pragma(inline, true); return (type == Type.Kw && kw == akw); }
  98   bool isKw (Keyword akw) { pragma(inline, true); return (type == Type.Kw && kw == akw); }
  99   bool isKw () { pragma(inline, true); return (type == Type.Kw); }
 100
 101 @property:
 102   const(char)[] str () { pragma(inline, true); return tkstr; }
 103   Keyword Kw () { pragma(inline, true); return (type == Type.Kw ? kw : Keyword.NoKW); }
 104   bool isId () { pragma(inline, true); return (type == Type.Id); }
 105   bool isStr () { pragma(inline, true); return (type == Type.Str); }
 106   bool isNum () { pragma(inline, true); return (type == Type.Num); }
 107   bool isSpec () { pragma(inline, true); return (type == Type.Spec); }
 108   bool isEOF () { pragma(inline, true); return (type == Type.EOF); }
 109 }
 110
 111
 112 // ////////////////////////////////////////////////////////////////////////// //
 113 public final class Lexer {
 114 private:
 115   const(char)[] text;
 116   uint tpos;
 117   Loc cpos; // position for last `getChar()`
 118   Loc pend; // end of previous token, for better error messages
 119   bool eof;
 120   bool lastWasEOL = true;
 121   Token[] lookup;
 122   Token tokeof; // will be fixed by `nextToken()`
 123
 124 public:
 125   this(T) (const(char)[] atext, T afname=null) if (is(T : const(char)[])) {
 126     text = atext;
 127     if (afname.length > 0) { static if (is(T == string)) cpos.file = afname; else cpos.file = afname.idup; }
 128     tokeof.loc.file = cpos.file;
 129     nextToken();
 130     pend.line = 1;
 131     pend.col = 1;
 132     pend.tpos = 0;
 133   }
 134
 135   void error (string msg, string file=__FILE__, usize line=__LINE__) {
 136     pragma(inline, true);
 137     throw new ErrorAt((lookup.length == 0 ? loc : lookup[0].loc), msg, null, file, line);
 138   }
 139
 140   static private void error (in ref Token tk, string msg, string file=__FILE__, usize line=__LINE__) {
 141     pragma(inline, true);
 142     throw new ErrorAt(tk.loc, msg, null, file, line);
 143   }
 144
 145   static private void error() (in auto ref Loc loc, string msg, string file=__FILE__, usize line=__LINE__) {
 146     pragma(inline, true);
 147     throw new ErrorAt(loc, msg, null, file, line);
 148   }
 149
 150   const(char)[] line (uint idx) {
 151     if (idx == 0) ++idx;
 152     uint pos = 0;
 153     while (--idx > 0) {
 154       while (pos < text.length && text.ptr[pos] != '\n') ++pos;
 155       ++pos;
 156     }
 157     if (pos >= text.length) return null;
 158     uint epos = pos;
 159     while (epos < text.length && text.ptr[epos] != '\n') ++epos;
 160     while (epos > pos && text.ptr[epos-1] <= ' ') --epos;
 161     return text[pos..epos];
 162   }
 163
 164   void popFront () {
 165     if (lookup.length > 0) {
 166       pend = lookup.ptr[0].eloc;
 167       ++pend.col; // for better error messages
 168       ++pend.tpos; // to be consistent
 169       foreach (immutable idx; 1..lookup.length) lookup.ptr[idx-1] = lookup.ptr[idx];
 170       lookup.length -= 1;
 171       lookup.assumeSafeAppend;
 172     }
 173     nextToken();
 174   }
 175
 176   @property pure nothrow @safe @nogc {
 177     bool empty () const { pragma(inline, true); return (lookup.length == 0); }
 178     ref inout(Token) front () inout { pragma(inline, true); return (lookup.length ? lookup.ptr[0] : tokeof); }
 179     // current token's loc
 180     auto loc () const { pragma(inline, true); return front.loc; }
 181     auto eloc () const { pragma(inline, true); return front.eloc; }
 182     auto peloc () const { pragma(inline, true); return pend; }
 183
 184     bool isId () const { pragma(inline, true); return front.isId; }
 185     bool isStr () const { pragma(inline, true); return front.isStr; }
 186     bool isNum () const { pragma(inline, true); return front.isNum; }
 187     bool isSpec () const { pragma(inline, true); return front.isSpec; }
 188   }
 189
 190   bool isKw (Keyword kw) const pure nothrow @safe @nogc { pragma(inline, true); return front.isKw(kw); }
 191   bool isKw () const pure nothrow @safe @nogc { pragma(inline, true); return front.isKw(); }
 192
 193   bool opEquals (Keyword kw) const pure nothrow @safe @nogc { pragma(inline, true); return (front == kw); }
 194
 195   // this eats keyword
 196   void expect (Keyword kw, string file=__FILE__, usize line=__LINE__) {
 197     if (!front.isKw(kw)) error(loc, "`"~keywordtext(kw)~"` expected", file, line);
 198     popFront();
 199   }
 200
 201   // this converts id to `string` via `.idup`, use with caution!
 202   // `.idup` is used to not anchor the whole source string
 203   string expectId (string msg="identifier expected", string file=__FILE__, usize line=__LINE__) {
 204     mustbeId(msg, file, line);
 205     auto res = lookup[0].istr;
 206     popFront();
 207     return res;
 208   }
 209
 210   // this converts id to `string` via `.idup`, use with caution!
 211   // `.idup` is used to not anchor the whole source string
 212   string expectStr (string msg="string expected", string file=__FILE__, usize line=__LINE__) {
 213     //pragma(inline, true);
 214     mustbeStr(msg, file, line);
 215     auto res = lookup[0].istr;
 216     popFront();
 217     return res;
 218   }
 219
 220   // `mustbe` doesn't eat token
 221   void mustbeType (Token.Type tp, string msg="identifier expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); return front.mustbeType(tp, msg, file, line); }
 222   void mustbeId (string msg="identifier expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); return front.mustbeId(msg, file, line); }
 223   void mustbeStr (string msg="string expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); return front.mustbeStr(msg, file, line); }
 224   void mustbeNum (string msg="number expected", string file=__FILE__, usize line=__LINE__) { pragma(inline, true); return front.mustbeNum(msg, file, line); }
 225
 226   bool eatKw (Keyword kw) {
 227     if (!isKw(kw)) return false;
 228     popFront();
 229     return true;
 230   }
 231
 232   ref Token peek (uint dist) {
 233     while (!eof && lookup.length <= dist) nextToken();
 234     return (dist < lookup.length ? lookup.ptr[dist] : tokeof);
 235   }
 236
 237   ref Token opIndex (usize dist) { pragma(inline, true); return peek(dist); }
 238
 239   // return loc for next `getChar()`
 240   Loc nextLoc () nothrow @safe @nogc {
 241     Loc res = cpos;
 242     if (lastWasEOL) { ++res.line; res.col = 1; } else ++res.col;
 243     return res;
 244   }
 245
 246   char peekChar (uint dist=0) nothrow @trusted @nogc {
 247     pragma(inline, true);
 248     return (tpos+dist >= text.length ? '\0' : (text.ptr[tpos+dist] ? text.ptr[tpos+dist] : ' '));
 249   }
 250
 251   // return char or 0
 252   char getChar () nothrow @trusted @nogc {
 253     if (tpos >= text.length) { tpos = text.length; eof = true; }
 254     if (eof) return '\0';
 255     cpos.tpos = tpos;
 256     char ch = text.ptr[tpos++];
 257     if (ch == '\0') ch = ' ';
 258     if (lastWasEOL) { ++cpos.line; cpos.col = 1; } else ++cpos.col;
 259     lastWasEOL = (ch == '\n');
 260     return ch;
 261   }
 262
 263   // skip blanks and comments
 264   //TODO: make special "comment" token(s)?
 265   void skipBlanks () @safe {
 266     mainloop: for (;;) {
 267       char ch = peekChar;
 268       if (ch == '/') {
 269         switch (peekChar(1)) {
 270           case '/': // single-line comment
 271             do { ch = getChar(); } while (ch != 0 && ch != '\n');
 272             continue mainloop;
 273           case '*': // multiline comment
 274             getChar(); // skip slash
 275             auto lc = cpos;
 276             getChar(); // skip star
 277             char pch = ' ';
 278             ch = ' '; // we need this
 279             for (;;) {
 280               pch = ch;
 281               ch = getChar();
 282               if (ch == 0) error(lc, "unterminated comment");
 283               if (ch == '/' && pch == '*') break;
 284             }
 285             continue mainloop;
 286           default:
 287         }
 288       }
 289       if (ch == 0 || ch > 32) return;
 290       getChar();
 291     }
 292   }
 293
 294   private void nextToken () {
 295     if (eof) return;
 296
 297     skipBlanks();
 298     if (peekChar == '\0') {
 299       eof = true;
 300       tokeof.loc = cpos;
 301       tokeof.eloc = cpos;
 302       //++tokeof.eloc.col; // for better error messages
 303       //++tokeof.eloc.tpos; // to be consistent
 304       return;
 305     }
 306
 307     Token tk;
 308     auto tkspos = tpos;
 309     char ch = getChar();
 310     tk.loc = cpos;
 311
 312     // quoted string
 313     if (ch == '"' || ch == '\'') {
 314       char ech = ch;
 315       tk.type = Token.Type.Str;
 316       ++tkspos; // skip quote
 317       for (;;) {
 318         ch = getChar();
 319         if (ch == 0) error(tk, "unterminated string");
 320         if (ch == ech) break;
 321       }
 322       tk.tkstr = text[tkspos..tpos-1]; // -1 due to eaten quote
 323       tk.eloc = cpos;
 324       //++tk.eloc.col; // for better error messages
 325       //++tk.eloc.tpos; // to be consistent
 326       lookup ~= tk;
 327       return;
 328     }
 329
 330     // hex number
 331     if (ch == '$') {
 332       float n = 0;
 333       tk.type = Token.Type.Num;
 334       getChar(); // skip dollar
 335       int dv = digitValue(peekChar);
 336       if (dv < 0 || dv > 15) error(tk, "hex number expected");
 337       for (;;) {
 338         dv = digitValue(peekChar);
 339         if (dv < 0 || dv > 15) break;
 340         n = n*16+dv;
 341         getChar();
 342       }
 343       ch = peekChar;
 344       if (isIdChar(ch) || ch == '.') error(tk, "hex number expected");
 345       tk.num = n;
 346       tk.tkstr = text[tkspos..tpos];
 347       tk.eloc = cpos;
 348       //++tk.eloc.col; // for better error messages
 349       //++tk.eloc.tpos; // to be consistent
 350       lookup ~= tk;
 351       return;
 352     }
 353
 354     // number
 355     if (isDigit(ch) || (ch == '.' && isDigit(peekChar))) {
 356       float n = 0;
 357       tk.type = Token.Type.Num;
 358       if (ch != '.') n = ch-'0';
 359       if (ch != '.') {
 360         // integral part
 361         for (;;) {
 362           if (!isDigit(peekChar)) break;
 363           ch = getChar();
 364           n = n*10+ch-'0';
 365         }
 366         if (peekChar == '.') ch = getChar();
 367       }
 368       if (ch == '.') {
 369         // fractional part
 370         if (!isDigit(peekChar)) error(tk, "real number expected");
 371         float div = 1;
 372         for (;;) {
 373           if (!isDigit(peekChar)) break;
 374           ch = getChar();
 375           div /= 10;
 376           n += div*(ch-'0');
 377         }
 378       }
 379       if (peekChar == 'e' || peekChar == 'E') {
 380         // exponent
 381         getChar();
 382         bool neg = false;
 383         if (peekChar == '+') getChar(); else if (peekChar == '-') { getChar(); neg = true; }
 384         if (!isDigit(peekChar)) error(tk, "invalid number");
 385         int e = 0;
 386         while (isDigit(peekChar)) {
 387           ch = getChar();
 388           e = e*10+(ch-'0');
 389           if (e < 0) error(tk, "invalid number (exponent overflow)");
 390         }
 391         //{ import std.conv : to; assert(0, to!string(e)); }
 392         if (neg) {
 393           while (e-- > 0) n = n/10;
 394         } else {
 395           while (e-- > 0) n = n*10;
 396         }
 397       }
 398       tk.num = n;
 399       tk.tkstr = text[tkspos..tpos];
 400       tk.eloc = cpos;
 401       //++tk.eloc.col; // for better error messages
 402       //++tk.eloc.tpos; // to be consistent
 403       ch = peekChar;
 404       if (isIdChar(ch) || ch == '.') error(tk, "invalid number");
 405       lookup ~= tk;
 406       return;
 407     }
 408
 409     // identifier
 410     if (isIdStart(ch)) {
 411       tk.type = Token.Type.Id;
 412       while (isIdChar(peekChar)) getChar();
 413       tk.tkstr = text[tkspos..tpos];
 414       tk.eloc = cpos;
 415       //++tk.eloc.col; // for better error messages
 416       //++tk.eloc.tpos; // to be consistent
 417       if (auto kw = tk.tkstr in keywords) {
 418         tk.type = Token.Type.Kw;
 419         tk.kw = *kw;
 420       }
 421       lookup ~= tk;
 422       return;
 423     }
 424
 425     // delimiter
 426     char[5] dbuf;
 427     dbuf[0] = ch;
 428     if (auto xkw = dbuf[0..1] in keywords) {
 429       tk.type = Token.Type.Kw;
 430       tk.kw = *xkw;
 431       foreach (uint dpos; 1..dbuf.length) {
 432         dbuf[dpos] = peekChar;
 433         if (auto kw = dbuf[0..dpos+1] in keywords) {
 434           tk.type = Token.Type.Kw;
 435           tk.kw = *kw;
 436           getChar(); // eat token char
 437         } else {
 438           break;
 439         }
 440       }
 441     } else {
 442       tk.type = Token.Type.Spec;
 443     }
 444     tk.tkstr = text[tkspos..tpos];
 445     tk.eloc = cpos;
 446     //++tk.eloc.col; // for better error messages
 447     //++tk.eloc.tpos; // to be consistent
 448     lookup ~= tk;
 449   }
 450
 451   auto select(RetType, string mode="peek", A...) (scope A args) { pragma(inline, true); return selectN!(RetType, mode)(0, args); }
 452
 453   auto selectN(RetType, string mode="peek", A...) (usize n, scope A args) {
 454     import std.traits : ReturnType;
 455
 456     static assert(mode == "peek" || mode == "pop" || mode == "pop-nondefault", "selectN: invalid mode: '"~mode~"'");
 457
 458     template isGoodDg(usize idx, T) {
 459       private import std.traits;
 460       static if (idx < A.length && isCallable!(A[idx]) && arity!(args[idx]) == 1) {
 461         enum isGoodDg = is(Parameters!(A[idx])[0] == T);
 462       } else {
 463         enum isGoodDg = false;
 464       }
 465     }
 466
 467     template isGoodArglessDg(usize idx) {
 468       private import std.traits;
 469       static if (idx < A.length && isCallable!(A[idx]) && arity!(args[idx]) == 0) {
 470         enum isGoodArglessDg = true;
 471       } else {
 472         enum isGoodArglessDg = false;
 473       }
 474     }
 475
 476     // sorry, but this has to be string mixin, due to possible empty `arg`
 477     enum DoCallDg(string arg) =
 478       "static if (!is(ReturnType!(A[xidx]) == void)) return cast(RetType)(args[xidx]("~arg~")); else { args[xidx]("~arg~"); return RetType.init; }";
 479
 480     // we can't have inner mixin templates, so... sorry, it's string again
 481     enum CallDg = q{
 482            static if (isGoodDg!(xidx, Token)) { mixin(DoCallDg!"tk"); }
 483       else static if (isGoodDg!(xidx, Loc)) { mixin(DoCallDg!"tk.loc"); }
 484       else static if (isGoodDg!(xidx, Token.Type)) { mixin(DoCallDg!"tk.type"); }
 485       else static if (isGoodDg!(xidx, Keyword)) { mixin(DoCallDg!"tk.Kw"); }
 486       else static if (isGoodArglessDg!(xidx)) { mixin(DoCallDg!""); }
 487       else static assert(0, "selectN: invalid delegate #"~xidx.stringof);
 488     };
 489
 490     auto tk = peek(n);
 491     bool found = false;
 492     foreach (immutable aidx, auto arg; args) {
 493       static if (aidx%2 == 0) {
 494         static if (is(typeof(arg) == Keyword) || is(typeof(arg) == Token.Type)) {
 495                static if (is(typeof(arg) == Keyword)) found = (tk == arg);
 496           else static if (is(typeof(arg) == Token.Type)) found = (tk.type == arg);
 497           else static assert(0, "wtf?!");
 498           if (found) {
 499             // process `mode`
 500             static if (mode != "peek") popFront();
 501             // call delegate
 502             enum xidx = aidx+1;
 503             mixin(CallDg);
 504           }
 505         } else {
 506           // default
 507           // process `mode`
 508           static if (mode == "pop") popFront();
 509           // call delegate
 510           enum xidx = aidx;
 511           mixin(CallDg);
 512         }
 513       }
 514     }
 515     error(tk, "selectN is out of nodes");
 516     assert(0);
 517   }
 518
 519 static:
 520   private immutable byte[256] digitValues = {
 521     byte[256] res = -1;
 522     foreach (ubyte idx; '0'..'9'+1) res[idx] = cast(byte)(idx-'0');
 523     foreach (ubyte idx; 'A'..'Z'+1) res[idx] = cast(byte)(idx-'A'+10);
 524     foreach (ubyte idx; 'a'..'z'+1) res[idx] = cast(byte)(idx-'a'+10);
 525     return res;
 526   }();
 527
 528   private immutable bool[256] idStartChars = {
 529     bool[256] res = false;
 530     foreach (ubyte idx; 'A'..'Z'+1) res[idx] = true;
 531     foreach (ubyte idx; 'a'..'z'+1) res[idx] = true;
 532     res['_'] = true;
 533     return res;
 534   }();
 535
 536   private immutable bool[256] idChars = {
 537     bool[256] res = false;
 538     foreach (ubyte idx; '0'..'9'+1) res[idx] = true;
 539     foreach (ubyte idx; 'A'..'Z'+1) res[idx] = true;
 540     foreach (ubyte idx; 'a'..'z'+1) res[idx] = true;
 541     res['_'] = true;
 542     return res;
 543   }();
 544
 545   bool isDigit() (char ch) { pragma(inline, true); return (ch >= '0' && ch <= '9'); }
 546   int digitValue() (char ch) { pragma(inline, true); return digitValues.ptr[cast(ubyte)ch]; }
 547   bool isIdStart() (char ch) { pragma(inline, true); return idStartChars.ptr[cast(ubyte)ch]; }
 548   bool isIdChar() (char ch) { pragma(inline, true); return idChars.ptr[cast(ubyte)ch]; }
 549
 550   string gmlQuote (const(char)[] s) {
 551     import std.array : appender;
 552     auto res = appender!string();
 553     enum Prev { Nothing, Char, Spec }
 554     Prev prev = Prev.Nothing;
 555     foreach (char ch; s) {
 556       if (ch < ' ' || ch == 127 || ch == '"') {
 557         import std.conv : to;
 558         final switch (prev) with (Prev) {
 559           case Nothing: break;
 560           case Char: res.put(`"+`); break;
 561           case Spec: res.put(`+`); break;
 562         }
 563         prev = Prev.Spec;
 564         res.put("chr(");
 565         res.put(to!string(cast(uint)ch));
 566         res.put(")");
 567       } else {
 568         final switch (prev) with (Prev) {
 569           case Nothing: res.put('"'); break;
 570           case Char: break;
 571           case Spec: res.put(`+"`); break;
 572         }
 573         prev = Prev.Char;
 574         res.put(ch);
 575       }
 576     }
 577     if (prev == Prev.Nothing) return `""`;
 578     if (prev == Prev.Char) res.put('"');
 579     return res.data;
 580   }
 581
 582   /// quote string: append double quotes, screen all special chars;
 583   /// so quoted string forms valid D string literal.
 584   /// allocates.
 585   string quote (const(char)[] s) {
 586     import std.array : appender;
 587     import std.format : formatElement, FormatSpec;
 588     auto res = appender!string();
 589     FormatSpec!char fspc; // defaults to 's'
 590     formatElement(res, s, fspc);
 591     return res.data;
 592   }
 593 }
 594
 595
 596 version(gml_lexer_test) unittest {
 597   import std.file;
 598   import std.stdio;
 599   auto s = readText("scrDrawHUD.gml");
 600   auto lex = new Lexer(s, "scrDrawHUD.gml");
 601   try {
 602     while (!lex.empty) {
 603       //if (lex == Keyword.RCurly) writeln("*******************");
 604       auto v = lex.select!(int, "pop")(
 605         Keyword.LCurly, (ref Token tk) => 1,
 606         Keyword.RCurly, (Keyword kw) => 2,
 607         Keyword.Semi, () => 6,
 608         Keyword.Sub, (Loc loc) => 99,
 609         Token.Type.Num, (ref Token tk) => 3,
 610         (ref Token tk) => writeln(tk),
 611       );
 612       if (v) writeln("*** ", v);
 613       //writeln(v, ": ", lex.front);
 614       //lex.popFront();
 615     }
 616   } catch (ErrorAt e) {
 617     writeln("PARSE ERROR: ", e.line);
 618     writeln(e.loc);
 619   }
 620 }