[started separate thread]
On Thu, 11 Nov 2010 00:58:31 +0100
Tomek Sowiński <j...@ask.me> wrote:
> Andrei Alexandrescu napisał:
>
> >> Speaking of getopt, when writing the 'grep' snippet I missed anonymous
> >> options a lot:
> >>
> >> bool h, i; string expr; string[] files;
> >> getopt(args, "h",&h, "i",&i,&expr,&files);
> >>
> >> They can be implemented with relatively little effort.
> >
> > Not getting the example. How would anonymous options work?
>
> // Let's match assignments.
> auto args = ["program.exe", ".*=.*;", "file1.d", "file2.d", "file3.d"];
> bool h, i; string expr; string[] files;
> getopt(args, "h",&h, "i",&i, &expr, &files);
> assert(!h);
> assert(!i);
> assert(expr == ".*=.*;");
> assert(files == ["file1.d", "file2.d", "file3.d"]);
> assert(args == ["program.exe"]);
>
> Staying conservative, anonymous options would only be allowed at the end of
> the
> option list, because their order matters (unlike named options). Perhaps this
> can
> be relaxed with time.
I thought once at a default interface between the command-line and a program's
startup routine, main(). The idea would be for main to have parameters
automagically fed from whatever the user provides. With a command-line syntax
inspired by named func call. It lets the program itself be called more or less
like a func, via program-level parameter definition:
// program "findword"
int main (string filename, string word, bool verbose=false) {...}
// use it
$ findword filename=foo.txt word=foo verbose=true
Parameters having default value can indeed be omitted by the user. Optionally,
the first arg (often corresponding to the "object" on which a command applies,
like the receiver in OO, and thus usually "obvious") can be automatically
mapped to the first param of main:
$ findword foo.txt word=foo
This is, indeed, a language-specific feature. On the other hand, it brings to
the user consistent program-call format -- rather than each program defining
its own. Maybe after sometime the same syntax trick and syntax would adopted by
other languages.
I find this very coool on the programmer side as well. It must indeed by
implemented in the language('s runtime) itself. To have such a feature without
breaking any code, a possibility may be to use a different name than "main", eg
"script".
(I guess such a feature would make some difference in judging a language's
adequacy to scripting.)
What do you think?
Denis
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