comp.lang.c Google Group

Re: 128 bit integer

2010-07-29T19:41:08Z

I'm not as familiar with IPv6 as I definitely should be, but I'll
extrapolate from IPv4.
[link]
[link]
Very superficially, you need fast bitand to see if an IP address matches a
route (an IP prefix): ip_addr & route_netmask == route_prefix. The route

Re: Random walk across array

2010-07-29T19:36:20Z

[...]
There are two different reasons why rand() % N might not be very
good. One is, as you say, the bucket problem that applies to all
possible rand() implementations. But the FAQ specifically mentions
another problem: "because the low-order bits of many random number
generators are distressingly non-random"; 13.18 covers this in

Re: KISS4691, a potentially top-ranked RNG.

2010-07-29T19:28:00Z

So for the put= values in fortran, you need a vector of pseudorandom
integers, which is as good as it gets without truly random devices,
making--one hopes-a period that is large with respect to the interval
you're interested in.
It doesn't seem like a problem with epistemology as much a mathematical

Re: zlib.h

2010-07-29T19:23:34Z

Oh. So "stream_t" is "char unsigned"? I guess knowing that I would have
written my previous followup very differently. Also, I seem to remember
"sizeof(stream_t)" expressions in your malloc() arguments. That's
completely superfluous -- sizeof(any character type) is per definition
((size_t)1). Why invent a new (and I'd risk, misleading, and also

Re: Yet another binary search tree library

2010-07-29T19:18:39Z

[...]
[...]
I think you meant LCM (least common multiple), not GCD (greatest
common divisor). For example, if two members of a struct have
alignments 4 and 6, the alignment of the struct is at least 12.
In practice, on most systems, all alignments are powers of two,
so the alignment of a struct is merely at least the largest of any

Re: Printing with fprintf on Win XP

2010-07-29T19:01:11Z

On Thu, 29 Jul 2010 16:53:56 +0100, Frederick Williams
The file pointer is null because fopen failed and you didn't check the
return value. It's caught by the assertions in the fprintf function.
In their infinite wisdom Microsoft didn't make printers a FILE device.
You can't fprintf to a printer device as you would a file or as you

Re: Printing with fprintf on Win XP

2010-07-29T18:53:45Z

[...]
[...]
And it's entirely possible that fopen() will succeed -- and create a
file called "USB001" in your current directory. If there is a special
file name that corresponds to your printer, you should read your
system's documentation to find out what that name is. Guessing is
unlikely to be a successful strategy.

Re: 128 bit integer

2010-07-29T18:45:24Z

I'm not as familiar with IPV6 as I probably should be. What benefit
does using, say, uint128_t to store IPV6 address give you over using,
say, unsigned char[16]? (Or wrap the array in a struct so you can do
assignment and equality comparison.)
In other words, how much sense does it make to do arithmetic in IPV6

Re: 128 bit integer

2010-07-29T18:27:35Z

You caught one of the obvious ones. The one that leapt out at me, of
course, was IPV6.
-s

Re: Macro function syntax

2010-07-29T18:14:05Z

...
It's not a bad idea, and it's probably what I'll be doing. It just
seems that there has to be a better way, a C function macro should be
able to act like a function. I just want the code to look like a
function call, since the called routines are often functions.
However, some of the time, they are not functions, or the function

Re: Macro function syntax

2010-07-29T18:07:50Z

<snip>
What other bits of C99 can you use? If you can use compound literals
you can turn the macro into a expression provided that you can change
buildlist to return a pointer to its list:
#define LINKX(routine, flags, ...)\
zlink((routine), (flags),\
buildlist((unsigned int[MAXARGS]){0}, __VA_ARGS__));

Re: Printing with fprintf on Win XP

2010-07-29T18:07:51Z

This really isn't a C question, as it's really a Windows and LaserJet p1006
question.
I doubt that the debugger is complaining that the strings "USB001:" et al
are "null". More likely, you mean that the return from fopen() is NULL when
passed those filenames.
Going on that assumption, add:
p = fopen("whatever", "w");

Re: 128 bit integer

2010-07-29T18:00:54Z

The use for it is rather obvious. For example, if your program uses
64-bit integers, then every time you multiply these integers, you have
to perform that multiplication within a 128-bit type. You have a
rectangle, whose coordinates are 64-bit integers? Well, then the the
area of that rectangle is a 128-bit integer, whether you like it or not.

Re: Macro function syntax

2010-07-29T17:41:19Z

[... putting back snipped context ...]
[...]
>
[...]
Place the "return value" as the first parameter, rather than the last.
Now, this goes against many people's coding standards, as it hides the fact
that it's going to change the value of that first parameter, but it does "work".
You could "unhide" this a little, by putting:

Re: Macro function syntax

2010-07-29T17:40:14Z

Why not put the return value as a LINKX argument before the valist?
as in
...
returnvar = zlink((routine),(falgs),list);
Usage:
LINKX(module2,flag2,returnvalu e2,4,5,6,7,8,9);
This is what pete was suggesting I'd guess, why did you think it a bad
idea?
-David