If computers do one thing well it is performing tasks very quickly. One thing computers do even better is performing the same task over and over again until specific criteria are met (or even infinitely if that is what is required). One this that computers are very bad at, however, is doing anything without being told to do it. Given these facts, it should come as no surprise that just about every programming language, Ruby included, provide mechanisms for instructing a computer system to repeat tasks.
 
If computers do one thing well it is performing tasks very quickly. One thing computers do even better is performing the same task over and over again until specific criteria are met (or even infinitely if that is what is required). One this that computers are very bad at, however, is doing anything without being told to do it. Given these facts, it should come as no surprise that just about every programming language, Ruby included, provide mechanisms for instructing a computer system to repeat tasks.
   Exception encountered, of type "Error"
[93064743] /index.php?diff=3872&oldid=3862&title=Ruby_While_and_Until_Loops Error from line 434 of /var/www/techotopia/includes/diff/DairikiDiff.php: Call to undefined function each()
Backtrace:
#0 /var/www/techotopia/includes/diff/DairikiDiff.php(544): DiffEngine->diag()
#1 /var/www/techotopia/includes/diff/DairikiDiff.php(344): DiffEngine->compareSeq()
#2 /var/www/techotopia/includes/diff/DairikiDiff.php(227): DiffEngine->diffLocal()
#3 /var/www/techotopia/includes/diff/DairikiDiff.php(721): DiffEngine->diff()
#4 /var/www/techotopia/includes/diff/DairikiDiff.php(859): Diff->__construct()
#5 /var/www/techotopia/includes/diff/DairikiDiff.php(980): MappedDiff->__construct()
#6 /var/www/techotopia/includes/diff/TableDiffFormatter.php(194): WordLevelDiff->__construct()
#7 /var/www/techotopia/includes/diff/DiffFormatter.php(140): TableDiffFormatter->changed()
#8 /var/www/techotopia/includes/diff/DiffFormatter.php(82): DiffFormatter->block()
#9 /var/www/techotopia/includes/diff/DifferenceEngine.php(881): DiffFormatter->format()
#10 /var/www/techotopia/includes/diff/DifferenceEngine.php(797): DifferenceEngine->generateTextDiffBody()
#11 /var/www/techotopia/includes/diff/DifferenceEngine.php(728): DifferenceEngine->generateContentDiffBody()
#12 /var/www/techotopia/includes/diff/DifferenceEngine.php(662): DifferenceEngine->getDiffBody()
#13 /var/www/techotopia/includes/diff/DifferenceEngine.php(632): DifferenceEngine->getDiff()
#14 /var/www/techotopia/includes/diff/DifferenceEngine.php(453): DifferenceEngine->showDiff()
#15 /var/www/techotopia/includes/page/Article.php(797): DifferenceEngine->showDiffPage()
#16 /var/www/techotopia/includes/page/Article.php(508): Article->showDiffPage()
#17 /var/www/techotopia/includes/actions/ViewAction.php(44): Article->view()
#18 /var/www/techotopia/includes/MediaWiki.php(490): ViewAction->show()
#19 /var/www/techotopia/includes/MediaWiki.php(287): MediaWiki->performAction()
#20 /var/www/techotopia/includes/MediaWiki.php(714): MediaWiki->performRequest()
#21 /var/www/techotopia/includes/MediaWiki.php(508): MediaWiki->main()
#22 /var/www/techotopia/index.php(41): MediaWiki->run()
#23 {main}