🚀 go-pugleaf

In article <4kobun$8i2@solutions.solon.com>,
Sean 'Captain Napalm' Conner <spc@gate.net> wrote:
>  But there is a potential problem with doing this.  What if you use a
>pre-compiled module that has extended printf(), say, using '%#' (unbeknownst
>to you, the documentation may be a bit lax (happens enough)).  What happens
>when you try to extend printf() using '%#'?  With possible different
>semantics (different type, say)?

That's why mine is not like the plan 9 fmtinstall().  In my current design,
assuming that we have
	typedef int (*fmtconv)();
(args will vary as I struggle with the design), you install a format with
	fmtconv format(int c, fmtconv);

which installs a new format and returns the previous one.  There are special
magic fmtconvs called FMT_IGN (to make a character no longer a format
character), FMT_DFL (to reset to the default), and FMT_GET, which doesn't
install anything, but returns the current conversion func.

This has been described as overengineering, but is there for precisely
that reason.

%# would be a poor choice; the conversion func for %# is one which returns
a magic cookie to set the alternate format flag.  :)

But yeah, I've been thinking about it.

>  -spc (Or does your printf() report a redefinition error?)

Nope.

I'm also considering the sfio magic of
	%(foo)
calling a conversion func attached to the string "foo".  This seems
frivolous for small apps, but if you look at a POSIX system, with
N+1 magic types like uid_t and gid_t, it might be useful.

I've been starting to get dazzled by the vast array of cool ideas
various previous implementations have come up with.  sfio has a base
flag, which could make the lives of thousands of first year students much
easier.

The problem is mostly coming up with a consistent way of parsing
things such that no currently standardized call to printf will change
behavior unless you've done something else (like call format()) which
is not standardized.

(Well, that would be trivial; but doing that and providing useful extensions
is more difficult.)

-s
-- 
Peter Seebach - seebs@solon.com - Copyright 1996 Peter Seebach.
C/Unix wizard -- C/Unix questions? Send mail for help.  No, really!
FUCK the communications decency act.  Goddamned government.  [literally.]
The *other* C FAQ - http://www.solon.com/~seebs/c/c-iaq.html