Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #58212

Re: New directions in C: Default arguments

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: New directions in C: Default arguments
Date 2015-03-16 08:35 -0700
Organization None to speak of
Message-ID <87mw3d0xcl.fsf@kst-u.example.com> (permalink)
References (5 earlier) <329f010e-821d-4c60-813a-949094e6e3be@googlegroups.com> <8953aa43-c9e1-471e-a763-c0d4c7fcc43b@googlegroups.com> <3f5b38ce-dd98-4ba6-b7a7-0ab9e8b89d44@googlegroups.com> <14f98f84-8033-4b26-ada1-305d89491e7e@googlegroups.com> <me51nf$2ha$1@dont-email.me>

Show all headers | View raw

Bartc <bc@freeuk.com> writes:
> On 15/03/2015 22:03, fir wrote:
>> besides that remarks (that ere heavily partial) one there could
>> consider a bot more general form (mentioned) with any interface to
>> called functions (rest is default)
>>
>> //foo has 17 args
>>
>> foo(x=10, y=30); // 15 other args are default
>>
>> foo(txt="aaa", y=30, z=12);// etc
>>
>> can be done and could be considered usefull but seems probably wastefull
>> (not c style , though may be some uglier api style like microsoft etc)
>
> Presumably the C style is to have to put in all 17 parameters, usually
> without annotation, which means studying the function docs while
> writing it (and still having to count along to see which argument is
> which), and again when someone else is trying to read it.
>
> Defaults arguments and keyword parameters are fairly straightforward
> enhancements, they are easy to implement (I've done it), and easy for
> users to grasp. In other words, a no-brainer.
>
> However, I believe the proposal in this thread is to only have default
> arguments, and to only allow trailing arguments to be omitted. Still
> useful, but keyword parameters thrown in would have been good too.

One problem with keyword parameters is that C doesn't require consistent
parameter names in all declarations.  Parameter names are not part of
the "signature" of a function (because in current C they're irrelevant
to the caller).

For example, given a definition like:

    void func(int x, int y) { /* ... */ }

any of these declarations would be compatible:

    void func(int, int);
    void func(int x, int y);
    void func(int y, int x);

Probably the simplest rule (that would not break existing code) would be
to make named parameters consistent with the most recent visible
declaration.

I'm ignoring old-style non-prototype declarations and definitions.
If default and/or named arguments were added to the language,
presumably they would *not* be supported for old-style definitions
and declarations.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

New directions in C: Default arguments jacob navia <jacob@spamsink.net> - 2015-03-14 23:11 +0100
  Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-14 18:17 -0700
    Re: New directions in C: Default arguments Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-15 11:25 +0000
      Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 07:18 -0700
        Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-15 14:32 +0000
          Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 08:30 -0700
            Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 09:05 -0700
              Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 10:15 -0700
                Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 15:03 -0700
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-15 22:40 +0000
                Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 16:04 -0700
                Re: New directions in C: Default arguments Keith Thompson <kst-u@mib.org> - 2015-03-16 08:35 -0700
                Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 16:45 +0100
                Re: New directions in C: Default arguments Keith Thompson <kst-u@mib.org> - 2015-03-16 11:36 -0700
                Re: New directions in C: Default arguments Philip Lantz <prl@canterey.us> - 2015-03-17 02:09 -0700
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-17 12:44 +0000
                Re: New directions in C: Default arguments Philip Lantz <prl@canterey.us> - 2015-03-17 11:07 -0700
                Re: New directions in C: Default arguments Martin Shobe <martin.shobe@yahoo.com> - 2015-03-16 11:35 -0500
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 17:07 +0000
                Re: New directions in C: Default arguments Martin Shobe <martin.shobe@yahoo.com> - 2015-03-16 12:40 -0500
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 18:12 +0000
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 18:30 +0000
                Re: New directions in C: Default arguments Martin Shobe <martin.shobe@yahoo.com> - 2015-03-16 13:52 -0500
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 19:35 +0000
                Re: New directions in C: Default arguments Martin Shobe <martin.shobe@yahoo.com> - 2015-03-16 14:52 -0500
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 20:27 +0000
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 19:44 +0000
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 19:55 +0000
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 20:23 +0000
                Re: New directions in C: Default arguments Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 20:53 +0000
                Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-16 14:33 -0700
                Re: New directions in C: Default arguments Keith Thompson <kst-u@mib.org> - 2015-03-16 11:44 -0700
                Re: New directions in C: Default arguments Martin Shobe <martin.shobe@yahoo.com> - 2015-03-16 13:59 -0500
  Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-15 01:33 +0000
    Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 00:59 -0700
    Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-15 23:45 +0100
      Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-15 16:21 -0700
        Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 11:41 +0100
          Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 11:13 +0000
            Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 13:19 +0100
              Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 12:38 +0000
                Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 13:51 +0100
                Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 13:21 +0000
                Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 15:12 +0100
                Re: New directions in C: Default arguments Richard Heathfield <rjh@cpax.org.uk> - 2015-03-16 14:24 +0000
                Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 16:09 +0100
                Re: New directions in C: Default arguments Richard Heathfield <rjh@cpax.org.uk> - 2015-03-16 18:11 +0000
                Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-17 13:23 +0100
                Re: New directions in C: Default arguments Richard Heathfield <rjh@cpax.org.uk> - 2015-03-17 12:28 +0000
                Re: New directions in C: Default arguments jacob navia <jacob@spamsink.net> - 2015-03-17 13:33 +0100
                Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-17 08:20 -0700
                Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-17 15:16 -0700
      Re: New directions in C: Default arguments jacob navia <jacob@spamsink.net> - 2015-03-16 11:38 +0100
        Re: New directions in C: Default arguments Bartc <bc@freeuk.com> - 2015-03-16 10:51 +0000
          Re: New directions in C: Default arguments raltbos@xs4all.nl (Richard Bos) - 2015-03-16 13:47 +0000
        Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-16 13:20 +0100
        Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-16 10:43 -0700
      Re: New directions in C: Default arguments David Brown <david.brown@hesbynett.no> - 2015-03-17 13:18 +0100
  Re: New directions in C: Default arguments bert <bert.hutchings@btinternet.com> - 2015-03-15 08:25 -0700
    Re: New directions in C: Default arguments jacob navia <jacob@spamsink.net> - 2015-03-15 18:16 +0100
  Re: New directions in C: Default arguments Michael Angelo Ravera <maravera@prodigy.net> - 2015-03-16 00:38 -0700
    Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-16 01:03 -0700
    Re: New directions in C: Default arguments Robert Wessel <robertwessel2@yahoo.com> - 2015-03-16 09:04 -0500
      Re: New directions in C: Default arguments Michael Angelo Ravera <maravera@prodigy.net> - 2015-03-17 00:22 -0700
        Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-17 01:08 -0700
          Re: New directions in C: Default arguments fir <profesor.fir@gmail.com> - 2015-03-19 01:37 -0700
            Re: New directions in C: Default arguments asetofsymbols@gmail.com - 2015-03-20 00:45 -0700
        Re: New directions in C: Default arguments Robert Wessel <robertwessel2@yahoo.com> - 2015-03-17 22:17 -0500
          Re: New directions in C: Default arguments Michael Angelo Ravera <maravera@prodigy.net> - 2015-03-18 15:55 -0700
  Re: New directions in C: Default arguments gwowen <gwowen@gmail.com> - 2015-03-16 01:07 -0700
    Re: New directions in C: Default arguments Keith Thompson <kst-u@mib.org> - 2015-03-16 08:18 -0700
      Re: New directions in C: Default arguments Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-16 17:35 +0000
      Definitions vs. Prototypes (Was: New directions in C: Default arguments) gazelle@shell.xmission.com (Kenny McCormack) - 2015-03-16 17:55 +0000
  Re: New directions in C: Default arguments Kaz Kylheku <kaz@kylheku.com> - 2015-03-16 20:21 +0000
    Re: New directions in C: Default arguments jacob navia <jacob@spamsink.net> - 2015-03-16 22:44 +0100

csiph-web