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Re: Return value for strcat and similar functions

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David Brown <david.brown@hesbynett.no> writes:

> On 10/05/15 17:44, Tim Rentsch wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>>
>>> On 08/05/15 00:39, Tim Rentsch wrote:
>>>> David Brown <david.brown@hesbynett.no> writes:
>>>>
>>>>> On 07/05/15 03:25, Tim Rentsch wrote:
>>>>>> David Brown <david.brown@hesbynett.no> writes:
>>>>>>
>>>>>>> Does anyone know why the return value for strcat and similar
>>>>>>> library functions is defined in such an unhelpful (IMHO) way?
>>>>>>>
>>>>>>> The return value of strcat(s1, s2) is always s1, which is a
>>>>>>> value you already have available.  Returning a pointer to the
>>>>>>> end of s1 (i.e., s1 + strlen(s1)) would be much more efficient
>>>>>>> when building up a string from parts.
>>>>>>
>>>>>> You're assuming that the value of the first argument is readily
>>>>>> available otherwise, which isn't always true - it could be the
>>>>>> result of a function call, for example.
>>>>>
>>>>> It /is/ readily available -
>>>>
>>>> Not exactly.  What you mean is not that it is readily available
>>>> but that it can be made available, by declaring a variable and
>>>> assigning the returned value.
>>>
>>> That is certainly what /I/ mean be "readily available".  You can
>>> get the value by simply attaching a name to it - that's good
>>> enough.
>>
>> I don't want to get into a quibbling match about definitions;
>> the key thing is your description is wrong.  You cannot simply
>> attach a name to the needed value - sometimes a name must be
>> declared before being assigned to.  That is a non-negligible
>> cost.
>
> If you think that this cost is non-negligible (assuming a
> half-decent compiler), then I suppose that explains your problem
> here.  [snip]

The cost I'm talking about is a coding and maintenance cost,
not a compilation or performance cost.  I don't mind agreeing to
the possibility that your sense of the size of that cost may be
different from mine.

>>>>> if you as a programmer need it, you have access to it.  If your
>>>>> "s1" is the result of calling "foo()", then all you need to write
>>>>> is "strcat(s1 = foo(), s2)".
>>>>
>>>> My point is either choice has its own advantages.  Personally I
>>>> think the choice made for strcat() is the right one for what it
>>>> is.  If something different or more elaborate is wanted, it's
>>>> easy enough to program that.
>>>
>>> I agree that it's easy to write a replacement for strcat() that
>>> returns a pointer to the end terminator (or the length of the
>>> string, if preferred).  And of course your personal opinion is up
>>> to you.  But I can't see any good reason why the standard library
>>> version is specified the way it is, rather than the much more
>>> useful alternative of returning a pointer to the end of the
>>> string.
>>
>> What's wrong with the idea that someone thought it valuable to
>> make the resulting (entire) string available so it could be
>> given, eg, as an argument to another function (or perhaps one
>> branch of a ?: operator, or return expression, etc), taking
>> advantage of a functional style?  Is it so hard for you to
>> imagine that someone else would have different priorities than
>> you do?
>
> The point of this thread was to ask people with different
> experiences and styles if they could think of an advantage of the
> way strcat is defined - precisely because while I could not think
> of one myself, I thought that someone else might.  So far no one
> (including you) has given any suggestions other than "it seemed a
> good idea at the time" or "they standardised the function they
> were using, without thinking about other use-cases".  [snip]

My answer may not have been stated very clearly, but I did
suggest another possible explanation, namely, for reasons you
don't consider important, namely coding convenience in certain
situations, those making the choice thought, and still think (or
would think, if they were still alive), that this consideration
outweighs those of the alternate semantics, even after conscious
evaluation.

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Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-06 10:02 +0200
  Re: Return value for strcat and similar functions Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2015-05-06 10:34 +0200
  Re: Return value for strcat and similar functions Lőrinczy Zsigmond <zsiga@nospam.for.me> - 2015-05-06 16:51 +0200
  Re: Return value for strcat and similar functions Keith Thompson <kst-u@mib.org> - 2015-05-06 08:58 -0700
    Re: Return value for strcat and similar functions Richard Heathfield <rjh@cpax.org.uk> - 2015-05-06 17:07 +0100
      Re: Return value for strcat and similar functions Morris Dovey <mrdovey@iedu.com> - 2015-05-06 12:01 -0500
    Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-07 10:19 +0200
      Re: Return value for strcat and similar functions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-07 13:21 +0000
        Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-07 16:24 +0200
          Re: Return value for strcat and similar functions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-07 18:02 +0000
      Re: Return value for strcat and similar functions Morris Dovey <mrdovey@iedu.com> - 2015-05-07 10:17 -0500
        Re: Return value for strcat and similar functions Morris Dovey <mrdovey@iedu.com> - 2015-05-07 10:56 -0500
          Re: Return value for strcat and similar functions asetofsymbols@gmail.com - 2015-05-07 11:00 -0700
            Re: Return value for strcat and similar functions Morris Dovey <mrdovey@iedu.com> - 2015-05-07 14:28 -0500
              Re: Return value for strcat and similar functions asetofsymbols@gmail.com - 2015-05-07 12:47 -0700
          Re: Return value for strcat and similar functions Nathan Wagner <nw@hydaspes.if.org> - 2015-05-08 09:31 +0000
        Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-07 15:55 -0700
        Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-08 11:03 +0200
          Re: Return value for strcat and similar functions Morris Dovey <mrdovey@iedu.com> - 2015-05-08 05:07 -0500
  Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-06 18:25 -0700
    Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-07 10:22 +0200
      Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-07 15:39 -0700
        Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-08 11:09 +0200
          Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-10 08:44 -0700
            Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-10 21:30 +0200
              Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-11 20:42 -0700
                Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-12 09:52 +0200
                Re: Return value for strcat and similar functions Bartc <bc@freeuk.com> - 2015-05-12 13:33 +0100
                Re: Return value for strcat and similar functions Ike Naar <ike@iceland.freeshell.org> - 2015-05-14 20:15 +0000
                Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-14 23:06 +0200
                Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-20 11:08 -0700
                Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-21 10:55 +0200
                Re: Return value for strcat and similar functions glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-21 13:05 +0000
                Re: Return value for strcat and similar functions David Brown <david.brown@hesbynett.no> - 2015-05-21 20:42 +0200
                Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-10 10:40 -0700
    Re: Return value for strcat and similar functions raltbos@xs4all.nl (Richard Bos) - 2015-05-08 21:56 +0000
      Re: Return value for strcat and similar functions Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-10 09:07 -0700
  Re: Return value for strcat and similar functions Bartc <bc@freeuk.com> - 2015-05-07 10:11 +0100

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