DZone Snippets: Minimiscience's Code Snippets

Tabs-to-space function

Minimiscience (Guildorn Tanaleth) — Fri, 06 Jul 2007 05:51:42 GMT

This Perl function returns its argument with any tabs it contained converted into the appropriate number of spaces.

sub tabs2space($) {

 my $str = shift;

 1 while $str =~ s/\t+/' ' x (length($&)*8 - length($`)%8)/e;

 return $str;

}

basename & dirname in Perl

Minimiscience (Guildorn Tanaleth) — Fri, 06 Jul 2007 05:49:34 GMT

These two Perl functions implement approximations of the UNIX utilities `basename` and `dirname`, though basename() automatically strips off the last extension no matter what.

sub basename($) {

 my $file = shift;

 $file =~ s!^(?:.*/)?(.+?)(?:\.[^.]*)?$!$1!;

 return $file;

}



sub dirname($) {my $file = shift; $file =~ s!/?[^/]*/*$!!; return $file; }

NetHack death statistics

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 07:29:51 GMT

This shell script reads in a NetHack logfile & outputs a list of all the things that have killed you, with their frequencies.

This script was originally posted to rec.games.roguelike.nethack by Faux_Pseudo.
grep killed /usr/games/lib/nethackdir/logfile | awk -F killed '{print"killed"$NF}' | sort | uniq -c | sort -r

Unicode chart

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 04:12:52 GMT

This PHP-enhanced HTML page will display the first 4,096 (unless you change it) Unicode characters in a neat table. Your browser's ability to render the characters properly may vary.







Unicode Chart











 for ($i=0; $i<256; $i++) { //DON'T try to generate the whole chart

  printf('', $i);

  for ($j=0; $j<16; $j++) {

   printf('', $i, $j);

  }

  echo "\n";

 }

?>


 0 1 2 3 4 5 6 7 8 9 A B C D E F
%04X &#x%X%X;

	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
%04X	&#x%X%X;

Image aggregator

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 04:08:17 GMT

This PHP snippet outputs the contents of a table (beginning & ending tags not included) containing all the images from the current directory.

 $columns = 3;

 $im = glob("*.{gif,jpg,png}", GLOB_BRACE);

 $rows = ceil(count($im) / $columns);

 for ($i = 0; $i < $rows; $i++) {

  echo "\n";

  for ($j = $columns*$i; isset($im[$j]) && $j - $columns*$i < $columns; $j++) {

   echo "$im[$j]
";

  }

  echo "";

 }

?>

Fibonacci function

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:54:06 GMT

This function returns the nth Fibonacci number, though most platforms can go no higher than the 47th.



int Fibonacci(int n) {

 int a = 1, b = 1, c, i;

 for (i=3; i<=n; i++) {c = b; b += a; a = c; }

 return b;

}

Factorial function

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:50:14 GMT

A (non-recursive) factorial function

int factorial(int x) {

 int fac = 1;

 for (int i=2; i<=x; i++) fac *= i;

 return fac;

}

Also, with this function defined, you can use two macros for calculating combinations & permutations:

#define nCr(n, r) (factorial(n) / factorial(n-r) / factorial(r))

#define nPr(n, r) (factorial(n) / factorial(n-r))

Modular inverse function

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:42:06 GMT

This function calculates & returns the inverse of a modulo n, both of which should be positive. If the inverse does not exist, 0 is returned. If you don't know what this means, don't bother.



int modInverse(int a, int n) {

 int i = n, v = 0, d = 1;

 while (a>0) {

  int t = i/a, x = a;

  a = i % x;

  i = x;

  x = d;

  d = v - t*x;

  v = x;

 }

 v %= n;

 if (v<0) v = (v+n)%n;

 return v;

}

Greatest Common Denominator function

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:37:26 GMT

This function returns the greatest common denominator (GCD) of its arguments.



int gcd(int x, int y) {

 int a, b;

 if (x else if (x>y) {a = x; b = y; }

 else {return x; }

 do {

  int r = a % b;

  a = b;

  b = r;

 } while (b != 0);

 return a;

}

Code execution timer

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:27:35 GMT

These two bits of code can be used to record & output the execution time of a piece of code in microseconds. NOTE: The functions used here are only available on BSD-like systems (I think).



/* Put this line at the top of the file: */

#include 



/* Put this right before the code you want to time: */

struct timeval timer_start, timer_end;

gettimeofday(&timer_start, NULL);



/* Put this right after the code you want to time: */

gettimeofday(&timer_end, NULL);

double timer_spent = timer_end.tv_sec - timer_start.tv_sec + (timer_end.tv_usec - timer_start.tv_usec) / 1000000.0;

printf("Time spent: %.6f\n", timer_spent);