Given that UNIX, including networking, is almost entirely coded in C,
how come so many things are almost impossible in ordinary C? Examples:
Network and internet access, access to UNIX interprocess controls and
communication, locale determination, EBCDIC/ASCII discrimination, etc.
Almost all of these are easy in Perl. Why isn't there a mechanism like
perl modules to allow easy extentions for facilities like these? Isn't
anyone working on this problem? or is it all being left for proprietary
systems?
Sep 2 '08
223  7349 
On Sep 4, 10:45 pm, jacob navia <ja...@nospam.c omwrote:
Lassie wrote:
"jacob navia" <ja...@nospam.c omschreef in bericht
news:g9******** **@aioe.org...
Operator overloading is not an objective per se. It is a means of making
libraries that use lists, flexible arrays and other sequential
containers interoperable using the same notation:
data[2]
to acces the third element of a list/array/other
I really would not implement operator[] for a linked list. operator[]
has the semantics of being a random access operator. A linked list is
not a data stucture one would use when random access is needed and
operator[] would have to loop to the correct index every time which is
suddenly invisible from the programmer.
Well, if you are using a list and you need the nth element you will
have to start at the start and go to the nth. That is because of the
data structure used.
And if you need the three elements 'n', 'n+1' and 'n+2', do you search
or each of them from the start of the list (what operator[] would have
to do), or do you only write a loop to the first one, and access the
other two by following a link from the element you currently have?
>
When you see that you are accessing random elements you change your
declaration to a flexible array and you have more efficient random
access. And you do not need to change the code.
And when you find that you only access successive elements, you drop
the library that foolishly uses operator[] to access elements in a
linked list.
You would have to change the code, but you get a several orders of
magnitude performance gain in return.
>
--
jacob navia
Bart v Ingen Schenau
"Bart van Ingen Schenau" <Ba************ ********@ict.nl wrote in message
news:aa******** *************** ***********@d45 g2000hsc.google groups.com...
On Sep 4, 10:45 pm, jacob navia <ja...@nospam.c omwrote:
>Lassie wrote:
I really would not implement operator[] for a linked list. operator[]
>Well, if you are using a list and you need the nth element you will
have to start at the start and go to the nth. That is because of the
data structure used.
And if you need the three elements 'n', 'n+1' and 'n+2', do you search
or each of them from the start of the list (what operator[] would have
to do), or do you only write a loop to the first one, and access the
other two by following a link from the element you currently have?
And when you find that you only access successive elements, you drop
the library that foolishly uses operator[] to access elements in a
linked list.
I created a scripting language once with arrays implemented as a linked list
(actually, as a block of 8 elements).
This remembered the last visited element, so [] indexing was reasonably
quick provided the application acccessed the array more or less
sequentially.
For C which is used to array accesses taking a couple of machine
instructions, even doing this would be quite a performance hit. Memory
management would be far easier though.
But, if the alternative was to use a higher-level (interpreted) language for
the extra
flexibility, then C + linked-list arrays + []indexing could be viable.
--
Bartc
jacob navia <ja***@nospam.c omwrote:
la************@ siemens.com wrote:
That's not necessary -- committee meetings are open to the public.
If the public can afford the trip, obviously.
Obviously. Like I said, however, the committee does try to meet in
various locations to make it easier for people to attend, but we're
limited to locations where someone is willing to host us (which requires
a not insubstatial expense). As you can see from the committee's web
site, we've been pretty successful in the past:
<http://www.open-std.org/jtc1/sc22/wg14/www/meetings>
I proposed that they set up a web site or similar place
where we could propose things (since they do not bother
to read comp.std.c as I heard in that group in the last
discussion)
No answer.
That's because you proposed it in comp.std.c, which you already know
most committee members don't read! And the reason we don't do it is the
same as the reason most members don't read comp.std.c -- if we did, we
would be inundated with half-baked suggestions from dilettantes who
would expect us to spend time and effort seriously considering their
suggestions and providing detailed feedback on their merits and
demerits. We simply don't have the resources to do that. Insisting
that people expend a certain amount of time and money to actually attend
a meeting weeds out people who aren't serious and allows face-to-face
discussion which is far less rancorous and much more productive than
on-line discussions. It also increases the committee's resources to
help offset the increased work load.
Do you know where the next meeting is?
Next week in San Jose, CA, USA. The meeting schedule (as far as is
known) is posted on the above page. Meetings for next year have not
been finalized yet, but there are outstanding or pending invitations to
meet in Toronto, CA in April and Santa Cruz, CA, USA in October
(according to the minutes from the last meeting, which are also posted
on the web site).
--
Larry Jones
I don't NEED to compromise my principles, because they don't have
the slightest bearing on what happens to me anyway. -- Calvin
Richard Heathfield <rj*@see.sig.in validwrites:
jacob navia said:
>Ben Bacarisse wrote:
<snip>
>>Because
there is no agreed way to program a flexible array, a list or a map,
everyone writes their own, or uses a published one that is
incompatibl e with all the other published ones out there. It is often
a lot of work just to coax two libraries to work together.
That is why I have been insisting that we adopt the operator overloading
feature that would allow using the '[' and ']' notation for general
containers.
I don't think you're in a position to insist, are you? Not even Microsoft
is in a position to insist on a change to the C language. In fact, not
even Dennis Ritchie is in that position.
It is sometimes difficult to remember that what one person sees as an
obvious improvement, another person sees as a hideous wart. Putting
oneself in another person's position is a useful and informative
intellectual exercise. Think up a change to C that you would really NOT
like to see in the language, and you should get the idea.
By the way, I'm not particularly against the idea of introducing operator
overloading into C (although many people probably are). But
politicking
I would sooner boil my nuts in a vat of sun flower oil than agree that
operator overloading in C is a good idea.
about it in comp.lang.c isn't going to get you anywhere. It's the ISO
people, not us, that you have to convince, and they are going to take a
lot of convincing after the drubbing they took over C99.
--
"Nick Keighley" <ni************ ******@hotmail. comwrote in message
>
>>I don't think we will actually run out of integers with 64 bits. With 32
bits yes, you can't quite give one to everyone in the world. But 64 bits
aren't going to have that problem for a long time yet.
>so why did IPv6 use 128 bits?
maybe it wasn't well designed. I can't imagine they had more than 2^64 bytes
of memory installed.
OTOH it might have been a signals processing device. These don't really use
integers in the normal C sense of the term. The integers are representations
of real valued signals, and highly specialised.
--
Nick Keighley
Richard wrote:
I would sooner boil my nuts in a vat of sun flower oil than agree that
operator overloading in C is a good idea.
Should I send you olive oil maybe?
--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique http://www.cs.virginia.edu/~lcc-win32
On Sep 5, 1:45*pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>
wrote:
On Sep 4, 8:47*pm, "Malcolm McLean" <regniz...@btin ternet.comwrote :
"Richard Heathfield" <r...@see.sig.i nvalidwrote in message news
Malcolm McLean said:
>I trust you are now joining the campaign for 64 bit ints.
Why? They're legal already. In any case, one day they will be too small.
Think the campaign for real ale rather than the campaign to free the weed.
I don't think we will actually run out of integers with 64 bits. With 32
bits yes, you can't quite give one to everyone in the world. But 64 bits
aren't going to have that problem for a long time yet.
so why did IPv6 use 128 bits?
That's as in TCP/IP the internet protocol. "old" IP (v4) used 32-bit
addresses (usually shown in dotted notation eg. 192.12.0.1). Because
the
address space is sparsely used they started to run out of addresses.
Telephone numbers suffer from the same problem. Hence London (UK) got
renumbered *twice* in recent years.
One fix for the IP address problem was a "new" IP standard, v6 (no-one
knows what happened to v5 :-) ). Initially 64 bits was proposed.
According
to their model this would allow everyone on the planet to have an IP
address.
But looking the then rate of technological progress it was realised
they should allow multiple IP addresses per person. This has now
happened;
my home isn't particualrly technology dense but I have several
ip addresses. Hence they went for 128 bits which is expected to last
for
quite a while. So there is already an application that finds 64 bits
inadequate without the need for 16 exa-bytes of memory.
--
Nick Keighley
Nick Keighley wrote:
On Sep 5, 1:45 pm, Nick Keighley <nick_keighley_ nos...@hotmail. com>
>so why did IPv6 use 128 bits?
....
my home isn't particualrly technology dense but I have several
ip addresses. Hence they went for 128 bits which is expected to last
for
quite a while. So there is already an application that finds 64 bits
inadequate without the need for 16 exa-bytes of memory.
This is little to do with needing 128-bit integers. This application needs a
16-byte identifier for the same sorts of reasons that credit cards mostly
use 16-digit numbers.
And it's unlikely that IP addresses need ALU support for +, -, * and /
operations. Possibly logical operations but this can easily be achieved on a
64-bit CPU without having a 128-bit word length.
--
Bartc
Nick Keighley said:
<snip>
But looking the then rate of technological progress it was realised
they should allow multiple IP addresses per person. This has now
happened;
my home isn't particualrly technology dense but I have several
ip addresses. Hence they went for 128 bits which is expected to last
for
quite a while. So there is already an application that finds 64 bits
inadequate without the need for 16 exa-bytes of memory.
Furthermore, cryptographical ly-inclined programmers will happily take the
biggest ints you can give them, and then beg for still bigger ints.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
"Nick Keighley" <ni************ ******@hotmail. comwrote in message
>Telephone numbers suffer from the same problem. Hence London (UK) got
renumbered *twice* in recent years.
I'm of the opinon that 3074457345 telephones ought to be enough for anyone,
if 64 bit integers were distributed fairly instead of being hogged by the
rich nations.
--
Free games and programming goodies. http://www.personal.leeds.ac.uk/~bgy1mm This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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