% I have enclosed code.sty, which achieves 99% of what you want without
% the need for a separate preprocessor. At the start of your document
% you write "\makeatactive". From then on, inline code is written as @\x
% -> x_1 & y@. The only difference with what you are used to, is that
% instead of
%
% @
%   foo :: Int -> Int
%   foo = \n -> n+1
% @
%
% you have to write
%
% \begin{code}
%   foo :: Int -> Int
%   foo = \n -> n+1
% \end{code}
%
% and that you cannot use @ in \section{} and \caption{}. For the paper that occurred twice, in which case I had to replace @...@ b y \texttt{...}.
%
%
% code.sty  --- nice verbatim mode for code

% To get '@' use \verb+@+

\def\icode{%
    \relax\ifmmode\hbox\else\leavevmode\null\fi
    \bgroup
    %\begingroup
    \@noligs
    \verbatim@font
    \verb@eol@error
    \let\do\@makeother \dospecials
    \@vobeyspaces
    \frenchspacing
    \@icode}
\def\@icode#1{%
    \catcode`#1\active
    \lccode`\~`#1%
    \lowercase{\let~\icode@egroup}}
\def\icode@egroup{%
    %\endgroup}
    \egroup}

% The \makeatactive command:
% makes @ active, in such a way that @...@ behaves as \icode@...@:
{
\catcode`@=\active
\gdef\makeatactive{
     \catcode`@=\active \def@{\icode@}
     % Since @ becomes active, it has to be taken care of in verbatim-modes:
     \let\olddospecials\dospecials \def\dospecials{\do\@\olddospecials}}
}
% \gdef\makeatother{\g@remfrom@specials{\@}\@makeother\@}
\gdef\makeatother{\@makeother\@}

\newcommand\codetabwidth{42pt}
{\catcode`\^^I=\active%
\gdef\@vobeytab{\catcode`\^^I\active\let^^I\@xobeytab}}
\def\@xobeytab{\leavevmode\penalty10000\hskip\codetabwidth}

\begingroup \catcode `|=0 \catcode `[= 1
\catcode`]=2 \catcode `\{=12 \catcode `\}=12
\catcode`\\=12 |gdef|@xcode#1\end{code}[#1|end[code]]
|endgroup
\def\@code{\trivlist \item\relax
  \if@minipage\else\vskip\parskip\fi
  \leftskip\@totalleftmargin\rightskip\z@skip
  \parindent\z@\parfillskip\@flushglue\parskip\z@skip
  \@@par
  \@tempswafalse
  \def\par{%
    \if@tempswa
      \leavevmode \null \@@par\penalty\interlinepenalty
    \else
      \@tempswatrue
      \ifhmode\@@par\penalty\interlinepenalty\fi
    \fi}%
  \obeylines \verbatim@font \@noligs
  \let\do\@makeother \dospecials
  \everypar \expandafter{\the\everypar \unpenalty}%
}
\def\code{\@code \frenchspacing\@vobeytab\@vobeyspaces \@xcode}
\def\endcode{\if@newlist \leavevmode\fi\endtrivlist}