R. Brock Lynn wrote:
> I'm really a newbie to C programming, don't know jack about style, convention,
> etc. So I'd like comments on a little app I recently wrote.
OK.
> #define MAX(a,b) a > b ? a : b
> #define MIN(a,b) a < b ? a : b
1. Macro arguments should be bracketed, in case they are complex
expressions containing infix operators with a lower precedence than
the ones in the macro.
2. If the macro is an expression, it should usually be enclosed in
parentheses; if it consists of multiple statements, it should be a
compound statement (in braces).
[1 and 2 provide equivalent semantics to a function call].
3. min and max are usually lowercase, and conditionally defined, in
case they are already defined in some header file.
So, I would have written:
#ifndef max
#define max(a,b) ((a) > (b) ? (a) : (b))
#endif
#ifndef min
#define min(a,b) ((a) < (b) ? (a) : (b))
#endif
> char* usage = "\nRandomIt version 0.01, shell utility for generating
>pseudo-random numbers.\nCopyright (C) 1998 R. Brock Lynn <[EMAIL PROTECTED]>.
>RandomIt comes with\nABSOLUTELY NO WARRANTY; for details type `%s --warranty'. This
>is free\nsoftware, and you are welcome to redistribute it under certain
>conditions;\ntype `%s --license' for details.\n\nUsage: %s <start> <end>\n\nExample:
>%s 0 100\n(picks a random integer from 0 to 100 inclusive)\n\n<start> and <end>
>must be integers,\nor you will get strange results.\n\n" ;
>
> char* warranty =
>"\n----------------------------------------------------------------------------\n\nNO
>WARRANTY\n\nBECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
>FOR\nTHE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN\nOTHERWISE
>STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES\nPROVIDE THE PROGRAM
>\"AS IS\" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED\nOR IMPLIED, INCLUDING, BUT
>NOT LIMITED TO, THE IMPLIED WARRANTIES OF\nMERCHANTABILITY AND FITNESS FOR A
>PARTICULAR PURPOSE. THE ENTIRE RISK AS TO\nTHE QUALITY AND PERFORMANCE OF THE PROGRAM
>IS WITH YOU. SHOULD THE PROGRAM\nPROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
>NECESSARY SERVICING, REPAIR OR\nCORRECTION.\n\nIN NO EVENT UNLESS REQUIRED BY
>APPLICABLE LAW OR AGREED TO IN WRITING\nWILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY
>WHO MAY MODIFY AND/OR\nREDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
>FOR DAMAGES,\nINCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONS!
EQUENTIAL DAMAGES ARISING\nOUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING
BUT NOT LIMITED TO\nLOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED
BY YOU OR\nTHIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY
OTHER\nPROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
THE\nPOSSIBILITY OF SUCH
DAMAGES.\n\n----------------------------------------------------------------------------\n\n"
;
>
> char* license =
>"\n----------------------------------------------------------------------------\n\nGNU
> GENERAL PUBLIC LICENSE\n\n(This document also available via the Internet
>at\nhttp://www.gnu.org/copyleft/gpl.html)\n\nVersion 2, June 1991\n\nCopyright (C)
>1989, 1991 Free Software Foundation, Inc.\n59 Temple Place - Suite 330, Boston, MA
>02111-1307, USA\n\nEveryone is permitted to copy and distribute verbatim copies\nof
>this license document, but changing it is not allowed.\n\nPreamble\n\nThe licenses
>for most software are designed to take away your freedom to\nshare and change it. By
>contrast, the GNU General Public License is intended\nto guarantee your freedom to
>share and change free software--to make sure\nthe software is free for all its users.
>This General Public License applies\nto most of the Free Software Foundation's
>software and to any other program\nwhose authors commit to using it. (Some other Free
>Software Foundation\nsoftware is covered by the GNU Library!
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RRANTY FOR\nTHE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW
. EXCEPT WHEN\nOTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
PARTIES\nPROVIDE THE PROGRAM \"AS IS\" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED\nOR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF\nMERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO\nTHE
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DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR
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WRITING\nWILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
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;
It is common practice to format source code to 80 columns. You can
take advantage of the fact that adjacent string literals are
concatenated to split the string over multiple lines.
Constant strings would normally be declared as `static const char *'.
I.e.:
static const char* usage =
"\n"
"RandomIt version 0.01, shell utility for generating pseudo-random numbers.\n"
"Copyright (C) 1998 R. Brock Lynn <[EMAIL PROTECTED]>. RandomIt comes with\n"
"ABSOLUTELY NO WARRANTY; for details type `%s --warranty'. This is free\n"
"software, and you are welcome to redistribute it under certain conditions;\n"
"type `%s --license' for details.\n\n"
"Usage: %s <start> <end>\n\nExample: %s 0 100\n"
"(picks a random integer from 0 to 100 inclusive)\n\n"
"<start> and <end> must be integers,\nor you will get strange results.\n\n" ;
Whilst using %s to substitute argv[0] as the program name is
generally a good idea, using it repeatedly within a given string is a
bit messy (IMHO).
Also, I wouldn't have bothered embedding the copyright/warranty
information in the program, and particularly not in the `usage'
string. And I definitely wouldn't embed a complete copy of the GPL in
the program.
> /* Get basename of how the program was called,
> if argv[0] == "/this/is/the/path/to/the/prog" then we want "prog" */
> name = argv[0] + strlen ( argv[0] ) - 1 ;
> while ( name > argv[0] && *(name - 1) != '/' ) -- name ;
I wouldn't have bothered with this; most programs just use argv[0].
> switch ( argc ) {
>
> case 3: {
You don't have to enclose the cases of a switch statement within
braces.
> start = (long) MIN ( atoi ( argv[1] ) , atoi ( argv[2] ) ) ;
> end = (long) MAX ( atoi ( argv[1] ) , atoi ( argv[2] ) ) ;
I would have stored the results of atoi(argv[1]) and atoi(argv[2]) in
variables, rather than calling atoi() repeatedly.
> srand ( time ( 0 ) ) ;
The problems with this have already been pointed out by Jakob and
Dave.
> randy = ( (float) rand() / (float) RAND_MAX ) * ( end - start
>+ 1 ) + start ;
> printf ( "%d\n", randy ) ;
You don't really need to use floating point for this; RAND_MAX is
usually 2^15-1, so using
rand() * (end - start + 1) / RAND_MAX
should be OK.
> if ( ! strcmp ( argv[1], "--license" ) ) printf ( license ) ;
Personally, I avoid using `!strcmp(...)'; I find `strcmp(...) == 0' to
be more intuitive.
> My program does give an error on the printf saying it can't print long ints, or
> something, why is that? (it converts my longs to ints, how do I do a format
> statement for longs in printf?)
Use "%ld". It doesn't make any difference on an i386, where both int
and long are 32 bits.
--
Glynn Clements <[EMAIL PROTECTED]>
