\def\baselinestretch{2}
\def\setstretch#1{\renewcommand{\baselinestretch}{#1}}
\def\@setsize#1#2#3#4{\@nomath#1
\let\@currsize#1\baselineskip
#2\baselineskip\baselinestretch\baselineskip
\parskip\baselinestretch\parskip
\setbox\strutbox\hbox{\vrule height.7\baselineskip
depth.3\baselineskip width\z@}
\normalbaselineskip\baselineskip#3#4}
\skip\footins 20pt plus4pt minus4pt
\def\@xfloat#1[#2]{\ifhmode \@bsphack\@floatpenalty -\@Mii\else
\@floatpenalty-\@Miii\fi\def\@captype{#1}\ifinner
\@parmoderr\@floatpenalty\z@
\else\@next\@currbox\@freelist{\@tempcnta\csname ftype@#1\endcsname
\multiply\@tempcnta\@xxxii\advance\@tempcnta\sixt@@n
\@tfor \@tempa :=#2\do
{\if\@tempa h\advance\@tempcnta \@ne\fi
\if\@tempa t\advance\@tempcnta \tw@\fi
\if\@tempa b\advance\@tempcnta 4\relax\fi
\if\@tempa p\advance\@tempcnta 8\relax\fi
}\global\count\@currbox\@tempcnta}\@fltovf\fi
\global\setbox\@currbox\vbox\bgroup
\def\baselinestretch{1}\small\normalsize
\boxmaxdepth\z@
\hsize\columnwidth \@parboxrestore}
\long\def\@footnotetext#1{\insert\footins{\def\baselinestretch{1}\footnotesize
\interlinepenalty\interfootnotelinepenalty
\splittopskip\footnotesep
\splitmaxdepth \dp\strutbox \floatingpenalty \@MM
\hsize\columnwidth \@parboxrestore
\edef\@currentlabel{\csname p@footnote\endcsname\@thefnmark}\@makefntext
{\rule{\z@}{\footnotesep}\ignorespaces
#1\strut}}}
\def\singlespace{%
\vskip\parskip%
\vskip\baselineskip%
\def\baselinestretch{1}%
\ifx\@currsize\normalsize\@normalsize\else\@currsize\fi%
\vskip-\parskip%
\vskip-\baselineskip%
}
\def\endsinglespace{\par}
\def\spacing#1{\par%
\def\baselinestretch{#1}%
\ifx\@currsize\normalsize\@normalsize\else\@currsize\fi}
\def\endspacing{\par%
\vskip \parskip%
\vskip \baselineskip%
\endgroup%
\vskip -\parskip%
\vskip -\baselineskip%
\begingroup}
\def\onehalfspace{\spacing{1.5}}
\let\endonehalfspace=\endspacing
\def\doublespace{\spacing{2}}
\let\doublespace=\endspacing
\everydisplay{
\abovedisplayskip \baselinestretch\abovedisplayskip%
\belowdisplayskip \abovedisplayskip%
\abovedisplayshortskip \baselinestretch\abovedisplayshortskip%
\belowdisplayshortskip  \baselinestretch\belowdisplayshortskip}
