\newenvironment{while}{\medskip}{\medskip}

\def\whskip{\texttt{skip}}
\def\whass#1#2{\texttt{#1 := #2}}
\def\whcomp#1#2{#1\texttt{;} #2}
\def\whif#1#2#3{\texttt{if #1 then #2 else #3 endif}}
\def\whwhile#1#2{\texttt{while #1 do #2 done}}