lparser.c

一个2D电磁场FEM计算的VC++源程序

    default: {  /* constructor_part -> listfields */
    case_default:
      cd->n = listfields(ls);
      cd->k = 0;  /* list */
      break;
    }
  }
}


static void constructor (LexState *ls) {
  /* constructor -> '{' constructor_part [';' constructor_part] '}' */
  FuncState *fs = ls->fs;
  int line = ls->linenumber;
  int pc = luaK_code1(fs, OP_CREATETABLE, 0);
  int nelems;
  Constdesc cd;
  check(ls, '{');
  constructor_part(ls, &cd);
  nelems = cd.n;
  if (optional(ls, ';')) {
    Constdesc other_cd;
    constructor_part(ls, &other_cd);
    check_condition(ls, (cd.k != other_cd.k), "invalid constructor syntax");
    nelems += other_cd.n;
  }
  check_match(ls, '}', '{', line);
  luaX_checklimit(ls, nelems, MAXARG_U, "elements in a table constructor");
  SETARG_U(fs->f->code[pc], nelems);  /* set initial table size */
}

/* }====================================================================== */




/*
** {======================================================================
** Expression parsing
** =======================================================================
*/


static void simpleexp (LexState *ls, expdesc *v) {
  FuncState *fs = ls->fs;
  switch (ls->t.token) {
    case TK_NUMBER: {  /* simpleexp -> NUMBER */
      Number r = ls->t.seminfo.r;
      next(ls);
      luaK_number(fs, r);
      break;
    }
    case TK_STRING: {  /* simpleexp -> STRING */
      code_string(ls, ls->t.seminfo.ts);  /* must use `seminfo' before `next' */
      next(ls);
      break;
    }
    case TK_NIL: {  /* simpleexp -> NIL */
      luaK_adjuststack(fs, -1);
      next(ls);
      break;
    }
    case '{': {  /* simpleexp -> constructor */
      constructor(ls);
      break;
    }
    case TK_FUNCTION: {  /* simpleexp -> FUNCTION body */
      next(ls);
      body(ls, 0, ls->linenumber);
      break;
    }
    case '(': {  /* simpleexp -> '(' expr ')' */
      next(ls);
      expr(ls, v);
      check(ls, ')');
      return;
    }
    case TK_NAME: case '%': {
      var_or_func(ls, v);
      return;
    }
    default: {
      luaK_error(ls, "<expression> expected");
      return;
    }
  }
  v->k = VEXP;
  v->u.l.t = v->u.l.f = NO_JUMP;
}


static void exp1 (LexState *ls) {
  expdesc v;
  expr(ls, &v);
  luaK_tostack(ls, &v, 1);
}


static UnOpr getunopr (int op) {
  switch (op) {
    case TK_NOT: return OPR_NOT;
    case '-': return OPR_MINUS;
    default: return OPR_NOUNOPR;
  }
}


static BinOpr getbinopr (int op) {
  switch (op) {
    case '+': return OPR_ADD;
    case '-': return OPR_SUB;
    case '*': return OPR_MULT;
    case '/': return OPR_DIV;
    case '^': return OPR_POW;
    case TK_CONCAT: return OPR_CONCAT;
    case TK_NE: return OPR_NE;
    case TK_EQ: return OPR_EQ;
    case '<': return OPR_LT;
    case TK_LE: return OPR_LE;
    case '>': return OPR_GT;
    case TK_GE: return OPR_GE;
    case TK_AND: return OPR_AND;
    case TK_OR: return OPR_OR;
    default: return OPR_NOBINOPR;
  }
}


static const struct {
  char left;  /* left priority for each binary operator */
  char right; /* right priority */
} priority[] = {  /* ORDER OPR */
   {5, 5}, {5, 5}, {6, 6}, {6, 6},  /* arithmetic */
   {9, 8}, {4, 3},                  /* power and concat (right associative) */
   {2, 2}, {2, 2},                  /* equality */
   {2, 2}, {2, 2}, {2, 2}, {2, 2},  /* order */
   {1, 1}, {1, 1}                   /* logical */
};

#define UNARY_PRIORITY	7  /* priority for unary operators */


/*
** subexpr -> (simplexep | unop subexpr) { binop subexpr }
** where `binop' is any binary operator with a priority higher than `limit'
*/
static BinOpr subexpr (LexState *ls, expdesc *v, int limit) {
  BinOpr op;
  UnOpr uop = getunopr(ls->t.token);
  if (uop != OPR_NOUNOPR) {
    next(ls);
    subexpr(ls, v, UNARY_PRIORITY);
    luaK_prefix(ls, uop, v);
  }
  else simpleexp(ls, v);
  /* expand while operators have priorities higher than `limit' */
  op = getbinopr(ls->t.token);
  while (op != OPR_NOBINOPR && priority[op].left > limit) {
    expdesc v2;
    BinOpr nextop;
    next(ls);
    luaK_infix(ls, op, v);
    /* read sub-expression with higher priority */
    nextop = subexpr(ls, &v2, priority[op].right);
    luaK_posfix(ls, op, v, &v2);
    op = nextop;
  }
  return op;  /* return first untreated operator */
}


static void expr (LexState *ls, expdesc *v) {
  subexpr(ls, v, -1);
}

/* }==================================================================== */


/*
** {======================================================================
** Rules for Statements
** =======================================================================
*/


static int block_follow (int token) {
  switch (token) {
    case TK_ELSE: case TK_ELSEIF: case TK_END:
    case TK_UNTIL: case TK_EOS:
      return 1;
    default: return 0;
  }
}


static void block (LexState *ls) {
  /* block -> chunk */
  FuncState *fs = ls->fs;
  int nactloc = fs->nactloc;
  chunk(ls);
  luaK_adjuststack(fs, fs->nactloc - nactloc);  /* remove local variables */
  removelocalvars(ls, fs->nactloc - nactloc);
}


static int assignment (LexState *ls, expdesc *v, int nvars) {
  int left = 0;  /* number of values left in the stack after assignment */
  luaX_checklimit(ls, nvars, MAXVARSLH, "variables in a multiple assignment");
  if (ls->t.token == ',') {  /* assignment -> ',' NAME assignment */
    expdesc nv;
    next(ls);
    var_or_func(ls, &nv);
    check_condition(ls, (nv.k != VEXP), "syntax error");
    left = assignment(ls, &nv, nvars+1);
  }
  else {  /* assignment -> '=' explist1 */
    int nexps;
    check(ls, '=');
    nexps = explist1(ls);
    adjust_mult_assign(ls, nvars, nexps);
  }
  if (v->k != VINDEXED)
    luaK_storevar(ls, v);
  else {  /* there may be garbage between table-index and value */
    luaK_code2(ls->fs, OP_SETTABLE, left+nvars+2, 1);
    left += 2;
  }
  return left;
}


static void cond (LexState *ls, expdesc *v) {
  /* cond -> exp */
  expr(ls, v);  /* read condition */
  luaK_goiftrue(ls->fs, v, 0);
}


static void whilestat (LexState *ls, int line) {
  /* whilestat -> WHILE cond DO block END */
  FuncState *fs = ls->fs;
  int while_init = luaK_getlabel(fs);
  expdesc v;
  Breaklabel bl;
  enterbreak(fs, &bl);
  next(ls);
  cond(ls, &v);
  check(ls, TK_DO);
  block(ls);
  luaK_patchlist(fs, luaK_jump(fs), while_init);
  luaK_patchlist(fs, v.u.l.f, luaK_getlabel(fs));
  check_match(ls, TK_END, TK_WHILE, line);
  leavebreak(fs, &bl);
}


static void repeatstat (LexState *ls, int line) {
  /* repeatstat -> REPEAT block UNTIL cond */
  FuncState *fs = ls->fs;
  int repeat_init = luaK_getlabel(fs);
  expdesc v;
  Breaklabel bl;
  enterbreak(fs, &bl);
  next(ls);
  block(ls);
  check_match(ls, TK_UNTIL, TK_REPEAT, line);
  cond(ls, &v);
  luaK_patchlist(fs, v.u.l.f, repeat_init);
  leavebreak(fs, &bl);
}


static void forbody (LexState *ls, int nvar, OpCode prepfor, OpCode loopfor) {
  /* forbody -> DO block END */
  FuncState *fs = ls->fs;
  int prep = luaK_code1(fs, prepfor, NO_JUMP);
  int blockinit = luaK_getlabel(fs);
  check(ls, TK_DO);
  adjustlocalvars(ls, nvar);  /* scope for control variables */
  block(ls);
  luaK_patchlist(fs, luaK_code1(fs, loopfor, NO_JUMP), blockinit);
  luaK_patchlist(fs, prep, luaK_getlabel(fs));
  removelocalvars(ls, nvar);
}


static void fornum (LexState *ls, TString *varname) {
  /* fornum -> NAME = exp1,exp1[,exp1] forbody */
  FuncState *fs = ls->fs;
  check(ls, '=');
  exp1(ls);  /* initial value */
  check(ls, ',');
  exp1(ls);  /* limit */
  if (optional(ls, ','))
    exp1(ls);  /* optional step */
  else
    luaK_code1(fs, OP_PUSHINT, 1);  /* default step */
  new_localvar(ls, varname, 0);
  new_localvarstr(ls, "(limit)", 1);
  new_localvarstr(ls, "(step)", 2);
  forbody(ls, 3, OP_FORPREP, OP_FORLOOP);
}


static void forlist (LexState *ls, TString *indexname) {
  /* forlist -> NAME,NAME IN exp1 forbody */
  TString *valname;
  check(ls, ',');
  valname = str_checkname(ls);
  /* next test is dirty, but avoids `in' being a reserved word */
  check_condition(ls,
       (ls->t.token == TK_NAME && ls->t.seminfo.ts == luaS_new(ls->L, "in")),
       "`in' expected");
  next(ls);  /* skip `in' */
  exp1(ls);  /* table */
  new_localvarstr(ls, "(table)", 0);
  new_localvar(ls, indexname, 1);
  new_localvar(ls, valname, 2);
  forbody(ls, 3, OP_LFORPREP, OP_LFORLOOP);
}


static void forstat (LexState *ls, int line) {
  /* forstat -> fornum | forlist */
  FuncState *fs = ls->fs;
  TString *varname;
  Breaklabel bl;
  enterbreak(fs, &bl);
  next(ls);  /* skip `for' */
  varname = str_checkname(ls);  /* first variable name */
  switch (ls->t.token) {
    case '=': fornum(ls, varname); break;
    case ',': forlist(ls, varname); break;
    default: luaK_error(ls, "`=' or `,' expected");
  }
  check_match(ls, TK_END, TK_FOR, line);
  leavebreak(fs, &bl);
}


static void test_then_block (LexState *ls, expdesc *v) {
  /* test_then_block -> [IF | ELSEIF] cond THEN block */
  next(ls);  /* skip IF or ELSEIF */
  cond(ls, v);
  check(ls, TK_THEN);
  block(ls);  /* `then' part */
}


static void ifstat (LexState *ls, int line) {
  /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
  FuncState *fs = ls->fs;
  expdesc v;
  int escapelist = NO_JUMP;
  test_then_block(ls, &v);  /* IF cond THEN block */
  while (ls->t.token == TK_ELSEIF) {
    luaK_concat(fs, &escapelist, luaK_jump(fs));
    luaK_patchlist(fs, v.u.l.f, luaK_getlabel(fs));
    test_then_block(ls, &v);  /* ELSEIF cond THEN block */
  }
  if (ls->t.token == TK_ELSE) {
    luaK_concat(fs, &escapelist, luaK_jump(fs));
    luaK_patchlist(fs, v.u.l.f, luaK_getlabel(fs));
    next(ls);  /* skip ELSE */
    block(ls);  /* `else' part */
  }
  else
    luaK_concat(fs, &escapelist, v.u.l.f);
  luaK_patchlist(fs, escapelist, luaK_getlabel(fs));
  check_match(ls, TK_END, TK_IF, line);
}


static void localstat (LexState *ls) {
  /* stat -> LOCAL NAME {',' NAME} ['=' explist1] */
  int nvars = 0;
  int nexps;
  do {
    next(ls);  /* skip LOCAL or ',' */
    new_localvar(ls, str_checkname(ls), nvars++);
  } while (ls->t.token == ',');
  if (optional(ls, '='))
    nexps = explist1(ls);
  else
    nexps = 0;
  adjust_mult_assign(ls, nvars, nexps);
  adjustlocalvars(ls, nvars);
}


static int funcname (LexState *ls, expdesc *v) {
  /* funcname -> NAME [':' NAME | '.' NAME] */
  int needself = 0;
  singlevar(ls, str_checkname(ls), v);
  if (ls->t.token == ':' || ls->t.token == '.') {
    needself = (ls->t.token == ':');
    next(ls);
    luaK_tostack(ls, v, 1);
    luaK_kstr(ls, checkname(ls));
    v->k = VINDEXED;
  }
  return needself;
}


static void funcstat (LexState *ls, int line) {
  /* funcstat -> FUNCTION funcname body */
  int needself;
  expdesc v;
  next(ls);  /* skip FUNCTION */
  needself = funcname(ls, &v);
  body(ls, needself, line);
  luaK_storevar(ls, &v);
}


static void namestat (LexState *ls) {
  /* stat -> func | ['%'] NAME assignment */
  FuncState *fs = ls->fs;
  expdesc v;
  var_or_func(ls, &v);
  if (v.k == VEXP) {  /* stat -> func */
    check_condition(ls, luaK_lastisopen(fs), "syntax error");  /* an upvalue? */
    luaK_setcallreturns(fs, 0);  /* call statement uses no results */
  }
  else {  /* stat -> ['%'] NAME assignment */
    int left = assignment(ls, &v, 1);
    luaK_adjuststack(fs, left);  /* remove eventual garbage left on stack */
  }
}


static void retstat (LexState *ls) {
  /* stat -> RETURN explist */
  FuncState *fs = ls->fs;
  next(ls);  /* skip RETURN */
  if (!block_follow(ls->t.token))
    explist1(ls);  /* optional return values */
  luaK_code1(fs, OP_RETURN, ls->fs->nactloc);
  fs->stacklevel = fs->nactloc;  /* removes all temp values */
}


static void breakstat (LexState *ls) {
  /* stat -> BREAK [NAME] */
  FuncState *fs = ls->fs;
  int currentlevel = fs->stacklevel;
  Breaklabel *bl = fs->bl;
  if (!bl)
    luaK_error(ls, "no loop to break");
  next(ls);  /* skip BREAK */
  luaK_adjuststack(fs, currentlevel - bl->stacklevel);
  luaK_concat(fs, &bl->breaklist, luaK_jump(fs));
  /* correct stack for compiler and symbolic execution */
  luaK_adjuststack(fs, bl->stacklevel - currentlevel);
}


static int stat (LexState *ls) {
  int line = ls->linenumber;  /* may be needed for error messages */
  switch (ls->t.token) {
    case TK_IF: {  /* stat -> ifstat */
      ifstat(ls, line);
      return 0;
    }
    case TK_WHILE: {  /* stat -> whilestat */
      whilestat(ls, line);
      return 0;
    }
    case TK_DO: {  /* stat -> DO block END */
      next(ls);  /* skip DO */
      block(ls);
      check_match(ls, TK_END, TK_DO, line);
      return 0;
    }
    case TK_FOR: {  /* stat -> forstat */
      forstat(ls, line);
      return 0;
    }
    case TK_REPEAT: {  /* stat -> repeatstat */
      repeatstat(ls, line);
      return 0;
    }
    case TK_FUNCTION: {  /* stat -> funcstat */
      funcstat(ls, line);
      return 0;
    }
    case TK_LOCAL: {  /* stat -> localstat */
      localstat(ls);
      return 0;
    }
    case TK_NAME: case '%': {  /* stat -> namestat */
      namestat(ls);
      return 0;
    }
    case TK_RETURN: {  /* stat -> retstat */
      retstat(ls);
      return 1;  /* must be last statement */
    }
    case TK_BREAK: {  /* stat -> breakstat */
      breakstat(ls);
      return 1;  /* must be last statement */
    }
    default: {
      luaK_error(ls, "<statement> expected");
      return 0;  /* to avoid warnings */
    }
  }
}


static void parlist (LexState *ls) {
  /* parlist -> [ param { ',' param } ] */
  int nparams = 0;
  int dots = 0;
  if (ls->t.token != ')') {  /* is `parlist' not empty? */
    do {
      switch (ls->t.token) {
        case TK_DOTS: next(ls); dots = 1; break;
        case TK_NAME: new_localvar(ls, str_checkname(ls), nparams++); break;
        default: luaK_error(ls, "<name> or `...' expected");
      }
    } while (!dots && optional(ls, ','));
  }
  code_params(ls, nparams, dots);
}


static void body (LexState *ls, int needself, int line) {
  /* body ->  '(' parlist ')' chunk END */
  FuncState new_fs;
  open_func(ls, &new_fs);
  new_fs.f->lineDefined = line;
  check(ls, '(');
  if (needself) {
    new_localvarstr(ls, "self", 0);
    adjustlocalvars(ls, 1);
  }
  parlist(ls);
  check(ls, ')');
  chunk(ls);
  check_match(ls, TK_END, TK_FUNCTION, line);
  close_func(ls);
  pushclosure(ls, &new_fs);
}


/* }====================================================================== */


static void chunk (LexState *ls) {
  /* chunk -> { stat [';'] } */
  int islast = 0;
  while (!islast && !block_follow(ls->t.token)) {
    islast = stat(ls);
    optional(ls, ';');
    LUA_ASSERT(ls->fs->stacklevel == ls->fs->nactloc,
               "stack size != # local vars");
  }
}