For some reason even when I enable \DontPrintSemicolon there are still semicolons on lines with comments. This is in Algorithm2e version 3.9.
\documentclass[12pt]{article}
\usepackage[lined,boxed]{algorithm2e}% using version 3.9
\usepackage{amsmath}
\newcommand*{\DontPrintSemicolon}[0]{\dontprintsemicolon}%remove for 5.0
%define defaults for algorithm2e
\let \oriAlgorithm=\algorithm
\renewcommand{\algorithm}[2]{
\oriAlgorithm % Begin document
\SetLine
\DontPrintSemicolon
\SetKwComment{Comment}{}{}
\Titleofalgo{ #1 }
\caption{ #2 }
}
\newcommand*{\Set}[2]{ #1 $\gets$ #2 }
\newcommand*{\SetC}[3]{ #1 $\gets$ #2 \Comment*[r]{#3} }
\begin{document}
\begin{algorithm}{test}{test to show semicolons existence}
\SetC{$f$}{$true$}{Some comment}\;
\Set{$f$}{$\lnot f$}\;
\Return{$f$}\;
\end{algorithm}
\end{document}

algorithm2eversion 5.0? The only historic stable version available isalgorithm2e4.01. If you're stuck with usingalgorithm2e3.9, you should make that available somewhere (usuallyPastebin). – Werner Nov 08 '13 at 21:07