[PATCH 2/2] Generate correct json

[Linus Torvalds]

On Tue, Aug 26, 2014 at 11:24 AM, Gehad Elrobey <gehadelrobey at gmail.com> wrote:
> I think this can be done easily by just checking if the item is the last
> item in the array before putting the commas.

So, quite frankly, you guys need to learn a very clean and simple
model for outputting lists with separators.

The way to generate clean separators is to have a separator string
variable, and output it *before* the entry. And initialize it to empty
(or a prefix for the whole thing), and then in the loop just
unconditionally set it to the separator for the next entry.

For example, do something like this:

    char *separator = "\"tags\": [ \"";

    if (!list)
        return;

    do {
        put_string(b, separator);
        put_HTML_quoted(b, list->tag->name);
        separator = "\", \"";
        list = list->next;
    } while (list);
    put_string("\" ]");

is a clean and efficient way to generate something like this:

   "tags": [ "entry1", "entry2" ]

Note how it doesn't need any special cases or conditionals in the
code. There's no test for "is this the first/last entry". It
JustWorks(tm). The only special case is the empty list, which for
things like this does tend to need to be a special case regardless
(because you generally wouldn't want to output anything at all for
that case - no empty list, no brackets, no "tags", no nothing). Also
note that this shows how you can often combine the "first separator is
different" with the prefix you need, and make the initial part of the
string be that first "separator".

It's a very useful and simple coding pattern for things like this.

                Linus