aaronbloomfield/pdr — pull request #44 by mrecachinas (2014-08-12 00:26:25+00:00)
Title: Included Arithmetic expansion for fix for #18

Mentioned Arithmetic expansion syntax `$(( ... ))` along with expr.

Also, edited the Wikibook on Bash Scripting to include expr (assuming they accept the changes) - see http://en.wikibooks.org/w/index.php?title=Bash_Shell_Scripting#expr_.28deprecated.29.