On Mon, 23 Jun 2008, Johannes Schindelin wrote:
>
> Thinking about the recursive approach again, I came up with this POC:
"recursive" is pointless.
The problem with the current "parse_options()" is not that it's recursive
(although that has been claimed multiple times!.
The problem with parse_options() is that it's currently impossible to
write something that handles _partial_ cases.
Let me explain.
Look at cmd_apply() in builtin-apply.c. Notice how it currently absolutely
CANNOT sanely be turned into using "parse_options()", not because it needs
any "recursive" handling, but simply because it wants to do *incremental*
handling.
It should be perfectly possible to change that argument loop from
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
if (strcmp(arg, "-")) {
.. handle <stdin> ..
continue;
}
...
to doing something like this:
for (;;) {
const char *arg;
argc = parse_options(argc, argv,
options, usage, PARSE_OPT_STOP_AT_UNKNOWN);
if (!argc)
break;
arg = argv[1];
argv++;
argc--;
if (strcmp(arg, "-")) {
.. handle <stdin> ..
continue;
}
...
or whatever. See?
Could you handle that with callbacks? Of course. "You can solve any
problem in computer science with an added level of indirection". But would
it be simpler to convert existing users? Hell no.
Could you handle the "recursive" use of parse_options() in builtin-blame.c
by teaching it about recursion? Yes. But again, it's just _simpler_ to
just teach parse_options() to parse the things it knows about, and leave
the other things in place.
Linus
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