%% Requires packages
%%   ifthen
%%
%%   Configure before use, using:
%%     hslSetRenderer{yourrenderer}   (invoked for each line, should produce nr)
%%
%%   You can also invoke the current renderer via:
%%     hslInsertLine
%%
%%   The default renderer uses the marginnote package.

\makeatletter

\newcounter{hsl@@lineCounter}
\setcounter{hsl@@lineCounter}{1}

\newcounter{hsl@@columnCounter}
\setcounter{hsl@@columnCounter}{0}

\newcommand\hsl@@renderer[0]{\hsl@@defaultRenderer}
\newcommand\hsl@@defaultRenderer[0]{\hslLeftNote{\ttfamily\scriptsize{}\hfill\arabic{hsl@@lineCounter}\stepcounter{hsl@@lineCounter}}}

\newcommand\hslLeftNote[1]{\ifthenelse{\isodd{\thepage}}{\reversemarginpar\marginnote{#1}\reversemarginpar}{\marginnote{#1}}}

\newcommand\hslLineMark[0]{\ifthenelse{\equal{\value{hsl@@columnCounter}}{0}}{\hslInsertLine\stepcounter{hsl@@columnCounter}}{}}
\newcommand\hslNewLine[0]{\setcounter{hsl@@columnCounter}{0}}

\newcommand\hslInsertLine[0]{\hsl@@renderer{}}
\newcommand\hslSetRenderer[1]{\renewcommand\hsl@@renderer[0]{#1}}

\makeatother

%subst fromto b e t = "\>[" b "]{}\hslLineMark{}" t "{}\<[" e "]%'n"
%subst newline   	= "\hslNewLine{}\\'n"
%subst blankline    = "\hslNewLine{}\\[\blanklineskip]%'n"
%subst code a       = "\begin{hscode}\hslNewLine\SaveRestoreHook'n" a "\ColumnHook'n\end{hscode}\resethooks'n"