Parser modification

[N1ceL]

Hello, I really liked the idea of making the strongest scripting language (jit/ffi turns the language into a better one) with normal syntax. I've already fixed '++', '--' bug (not working without ';'), made arrays from 0, and etc. But for the perfect language I want to make 'for' like on JS/C++, but I do not know how to fix the problem is that the loop works incorrectly.

Parser 'for' code:

static void parse_for_new(LexState* ls, BCLine line)
{
    FuncState* fs = ls->fs;
    BCPos start, loop, condexit;
    FuncScope bl;
    lj_lex_next(ls);  /* Skip 'while'. */
    lex_check(ls, '(');
    parse_local(ls);
    lex_check(ls, ';');
    start = fs->lasttarget = fs->pc;
    condexit = expr_cond(ls);
    lex_check(ls, ';');
    parse_block(ls);
    lex_check(ls, ')');
    fscope_begin(fs, &bl, FSCOPE_LOOP);
    loop = bcemit_AD(fs, BC_LOOP, fs->nactvar, 0);
    parse_block(ls);
    jmp_patch(fs, bcemit_jmp(fs), start);
    fscope_end(fs);
    jmp_tohere(fs, condexit);
    jmp_patchins(fs, loop, fs->pc);
}

Here is a screenshot with the problem, the value changes between the 'for' check and the main block:

I do not know how to make a 'value change block' after 'main block'

[mingodad]

Can you share your project to see the whole thing ?

[N1ceL]

Created a repository, but temporarily I had to disable the second 'for' type (with 'in') because the problems with creating a variable in block between '(', ';'

[mingodad]

I'm looking at it now.

[mingodad]

It seems that the problem is that you are parsing then third parameter of the for statement but not skiping it when entering the loop, somehow you'll need add some jumps or reorder the generated code.

static void parse_for_new(LexState* ls, BCLine line)
{
    FuncState* fs = ls->fs;
    BCPos start, loop, condexit;
    FuncScope bl;
    lj_lex_next(ls);  /* Skip 'while'. */
    lex_check(ls, '(');
    parse_local(ls);
    lex_check(ls, ';');
    start = fs->lasttarget = fs->pc;
    condexit = expr_cond(ls);
    lex_check(ls, ';');
    parse_block(ls); ////!!!! this code block should be moved to the end of the loop
    lex_check(ls, ')');
    fscope_begin(fs, &bl, FSCOPE_LOOP);
    loop = bcemit_AD(fs, BC_LOOP, fs->nactvar, 0);
    parse_block(ls);
    jmp_patch(fs, bcemit_jmp(fs), start);
    fscope_end(fs);
    jmp_tohere(fs, condexit);
    jmp_patchins(fs, loop, fs->pc);
}

[N1ceL]

The problem is that I have no idea how to do it. Parsing is sequential, I don't know how to skip this block, and then go back to register it.

In Jual 'for' block with JS syntax looks like this: https://github.com/sajonoso/jual/blob/master/src/lparser.c#L1654-L1683
But how to make it on LuaJIT, I have no idea.

Anyway thank you for your time.

[mingodad]

Should be very similar, why not you try first with ljs following Jual then you go back to Ljslit, the jumps and lables are there:

  checknext(ls, ';');
  condinit = luaK_getlabel(fs); //creating a label for goto ?
  condexit = cond(ls);
  checknext(ls, ';');
  blockinit = luaK_jump(fs); // doing the goto ?
  stepinit = luaK_getlabel(fs); //creating another label
  statement(ls);
  stepexit = luaK_jump(fs); //anther goto
  checknext(ls, ')');
  checknext(ls, '{');
  luaK_patchtohere(fs, blockinit); //doing fixups
  block(ls);
  (void)luaK_getlabel(fs);
  luaK_jumpto(fs, stepinit); //goto
  luaK_patchtohere(fs, stepexit); 
  luaK_jumpto(fs, condinit); //goto
  check_match(ls, '}', TK_FOR, line);
  leaveblock(fs);
  luaK_patchtohere(fs, condexit); //adjusting the label address ?