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new semantics for "for" local variables

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This commit is contained in:
Roberto Ierusalimschy
2003-05-13 17:15:59 -03:00
parent c767747191
commit 6d268b0b00
5 changed files with 61 additions and 52 deletions
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44
lparser.c
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@@ -1,5 +1,5 @@
/*
** $Id: lparser.c,v 1.207 2003/02/28 17:19:47 roberto Exp roberto $
** $Id: lparser.c,v 1.208 2003/04/03 13:35:34 roberto Exp roberto $
** Lua Parser
** See Copyright Notice in lua.h
*/
@@ -1027,30 +1027,34 @@ static int exp1 (LexState *ls) {
static void forbody (LexState *ls, int base, int line, int nvars, int isnum) {
/* forbody -> DO block */
BlockCnt bl;
FuncState *fs = ls->fs;
int prep, endfor;
adjustlocalvars(ls, nvars); /* scope for all variables */
adjustlocalvars(ls, 3); /* control variables */
check(ls, TK_DO);
enterblock(fs, &bl, 1); /* loop block */
prep = luaK_getlabel(fs);
prep = luaK_codeAsBx(fs, (isnum ? OP_FORPREP : OP_TFORPREP), base, NO_JUMP);
enterblock(fs, &bl, 0); /* scope for declared variables */
adjustlocalvars(ls, nvars);
luaK_reserveregs(fs, nvars);
block(ls);
luaK_patchtohere(fs, prep-1);
leaveblock(fs); /* end of scope for declared variables */
luaK_patchtohere(fs, prep);
endfor = (isnum) ? luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP) :
luaK_codeABC(fs, OP_TFORLOOP, base, 0, nvars - 3);
luaK_codeABC(fs, OP_TFORLOOP, base, 0, nvars);
luaK_fixline(fs, line); /* pretend that `OP_FOR' starts the loop */
luaK_patchlist(fs, (isnum) ? endfor : luaK_jump(fs), prep);
leaveblock(fs);
luaK_patchlist(fs, (isnum ? endfor : luaK_jump(fs)), prep + 1);
}
static void fornum (LexState *ls, TString *varname, int line) {
/* fornum -> NAME = exp1,exp1[,exp1] DO body */
/* fornum -> NAME = exp1,exp1[,exp1] forbody */
FuncState *fs = ls->fs;
int base = fs->freereg;
new_localvar(ls, varname, 0);
new_localvarstr(ls, "(for index)", 0);
new_localvarstr(ls, "(for limit)", 1);
new_localvarstr(ls, "(for step)", 2);
new_localvar(ls, varname, 3);
check(ls, '=');
exp1(ls); /* initial value */
check(ls, ',');
@@ -1061,39 +1065,39 @@ static void fornum (LexState *ls, TString *varname, int line) {
luaK_codeABx(fs, OP_LOADK, fs->freereg, luaK_numberK(fs, 1));
luaK_reserveregs(fs, 1);
}
luaK_codeABC(fs, OP_SUB, fs->freereg - 3, fs->freereg - 3, fs->freereg - 1);
luaK_jump(fs);
forbody(ls, base, line, 3, 1);
forbody(ls, base, line, 1, 1);
}
static void forlist (LexState *ls, TString *indexname) {
/* forlist -> NAME {,NAME} IN explist1 DO body */
/* forlist -> NAME {,NAME} IN explist1 forbody */
FuncState *fs = ls->fs;
expdesc e;
int nvars = 0;
int line;
int base = fs->freereg;
/* create control variables */
new_localvarstr(ls, "(for generator)", nvars++);
new_localvarstr(ls, "(for state)", nvars++);
new_localvarstr(ls, "(for control)", nvars++);
/* create declared variables */
new_localvar(ls, indexname, nvars++);
while (testnext(ls, ','))
new_localvar(ls, str_checkname(ls), nvars++);
check(ls, TK_IN);
line = ls->linenumber;
adjust_assign(ls, nvars, explist1(ls, &e), &e);
adjust_assign(ls, 3, explist1(ls, &e), &e);
luaK_checkstack(fs, 3); /* extra space to call generator */
luaK_codeAsBx(fs, OP_TFORPREP, base, NO_JUMP);
forbody(ls, base, line, nvars, 0);
forbody(ls, base, line, nvars - 3, 0);
}
static void forstat (LexState *ls, int line) {
/* forstat -> fornum | forlist */
/* forstat -> FOR (fornum | forlist) END */
FuncState *fs = ls->fs;
TString *varname;
BlockCnt bl;
enterblock(fs, &bl, 0); /* block to control variable scope */
enterblock(fs, &bl, 1); /* scope for loop and control variables */
next(ls); /* skip `for' */
varname = str_checkname(ls); /* first variable name */
switch (ls->t.token) {
@@ -1102,7 +1106,7 @@ static void forstat (LexState *ls, int line) {
default: luaX_syntaxerror(ls, "`=' or `in' expected");
}
check_match(ls, TK_END, TK_FOR, line);
leaveblock(fs);
leaveblock(fs); /* loop scope (`break' jumps to this point) */
}