[PATCH] bc Version 1.1

[Denys Vlasenko]

On Mon, Dec 3, 2018 at 6:49 PM Denys Vlasenko <vda.linux at googlemail.com> wrote:
> On Sat, Nov 3, 2018 at 6:17 PM Gavin Howard <gavin.d.howard at gmail.com> wrote:
> > After making changes to the bc for Denys' requests, I have a better
> > version of the bc.
> >
> > This version, pasted at https://pastebin.com/0M9sMhtM and raw at
> > https://pastebin.com/raw/0M9sMhtM, has fulfilled every one of Denys'
> > requests except for a few.
>
> +static BcStatus bc_lex_comment(BcLex *l)
> +{
> +    size_t i, nls = 0;
> +    const char *buf = l->buf;
> +    bool end = false;
> +    char c;
> +
> +    l->t.t = BC_LEX_WHITESPACE;
> +
> +    for (i = ++l->i; !end; i += !end) {
> +
> +        for (c = buf[i]; c != '*' && c != 0; c = buf[++i]) nls += (c == '\n');
> +
> +        if (c == 0 || buf[i + 1] == '\0') {
> +            l->i = i;
> +            return BC_STATUS_LEX_NO_COMMENT_END;
> +        }
> +
> +        end = buf[i + 1] == '/';
> +    }
> This is rather unreadable.

After untangling unreadable for() statements and 'end' variable,
this is what it actually does:

{
        size_t i, nls = 0;
        const char *buf = l->buf;

        l->t.t = BC_LEX_WHITESPACE;
        i = ++l->i;
        for (;;) {
                for (;;) {
                        char c = buf[i];
                        if (c == '*')
                                break;
                        if (c == '\0') {
                                l->i = i;
                                return BC_STATUS_LEX_NO_COMMENT_END;
                        }
                        nls += (c == '\n');
                        i++;
                }
                i++;
                if (buf[i] == '\0') {
                        l->i = i - 1;
                        return BC_STATUS_LEX_NO_COMMENT_END;
                }
                if (buf[i] == '/')
                        break;
        }

and now, since inner for() has only one break, I can put
'/' check directly there, eliminating one for() altogether:

        for (;;) {
                char c = buf[i];
 check_star:
                if (c == '*') {
                        c = buf[++i];
                        if (c == '/')
                                break;
                        goto check_star;
                }
                if (c == '\0') {
                        l->i = i;
                        return BC_STATUS_LEX_NO_COMMENT_END;
                }
                nls += (c == '\n');
                i++;
        }

Now l->i on error might be different (+1) but this is likely should be that way.