Re: New directions in C: Default arguments

Newsgroups	comp.lang.c
From	Greg Martin <greg.at.softsprocket@dot.com>
Subject	Re: New directions in C: Default arguments
References	(9 earlier) <me51nf$2ha$1@dont-email.me> <87mw3d0xcl.fsf@kst-u.example.com> <me70mb$h53$1@dont-email.me> <_4ENw.20099$7U.13751@fx31.iad> <me76cp$b8d$1@dont-email.me>
Organization	SoftSprocket
Message-ID	<TiFNw.32006$IH4.11330@fx08.iad> (permalink)
Date	2015-03-16 18:30 +0000

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On 2015-03-16, Bartc <bc@freeuk.com> wrote:
> On 16/03/2015 17:07, Greg Martin wrote:
>> On 2015-03-16, Martin Shobe <martin.shobe@yahoo.com> wrote:
>
>>> For example (using . to identify keywords as seen else thread) the
>>> following would all be compatible.
>>>
>>> void func(int w, int x, int .y, int .z);
>>> void func(int x, int w, int .y, int .z);
>>> void func(int, int, int .y, int .z);
>>>
>>> However, the following would not be compatible with the above and would
>>> require a diagnostic if they both appeared in the same scope.
>>>
>>> void func(int w, int x, int .z, int .y);
>
>>
>> What would this buy you, over using a structure to pass the arguments?
>> I'm not sure it would be worth the effort.
>>
>> A structure as an argument allows some defaulting of arguments as well
>> as implicit named parameters. Admittedly the default arguments are
>> limited.
>
> You seriously think using a struct is nearly as good as using 
> named/default arguments? OK, let's look at the disadvantages of using 
> structs:
>

Specifically, to adding a separate syntax for the purpose.

> (1) You now have to create a corresponding struct for each of the 
> hundreds of functions you might want to use named arguments for.
>
> (2) You have to maintain a function parameter list *and* its struct.
>

No, that isn't the case at all - the parameter list is the structure.

> (3) Each function, especially if applying this retroactively to an 
> existing application, now has to be rewritten to use a single struct 
> argument.

As would be the case with new syntax. In addition all compilers would
have to support it for it to be of any value.

>
> (4) Within each function, each a, b, c, d parameter now has to be 
> written x.a, x.b, x.c, c.d etc.
>
> (5) You have the extra overheads of passing a struct by value.
>

Pass a pointer.

> (6) In the caller, you either have to declare and initialise a struct 
> separately, then pass it as fn(&s), which now becomes unreadable, or..
>
> (7) ...use the ugly compound literal syntax (Martin gave an example of 
> what that looks like.
>
> (8) You can't now /optionally/ use either normal arguments to a 
> function, or default/named parameters; it's all or nothing. Which means 
> if introducing this to an existing application, you have to rewrite it.
>

Yes and adding a new syntax means rewriting the code as well.

> (9) As you pointed out, you don't have much choice about default values 
> (actually I'm not even sure that 0 is guaranteed with compound literals).
>
> (10) In all, it will be such a painful, ungainly and unreadable way of 
> doing it, that no-one will bother.
>

It has the value of currently being possible and I believe people do
pass structs, or at least pointers to said, as arguments.

> Of course using proper named/default arguments has its own disadvantage:
>
> (1) You have to name the parameters in the function prototype, if one is 
> used.
>
> Once done however, you don't have to change anything else; you can 
> optionally use the feature on a call-by-call basis. It is also easier to 
> write, more readable, and requires little maintenance beyond what is 
> needed anyway when a function interface changes.
>

Not if a new syntax is introduced.

-- 
http://www.softsprocket.com

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

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