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% Filename: Lambda.sty
% Author: Alan Jeffrey
% Last modified: 12 Feb 1990
%
% This style is (c) 1990 Alan Jeffrey. Permission is granted to make
% copies, as long as
%
% a) no deletions are made,
%
% b) all additions are clearly marked, in amongst all this header information,
% *and* where the addition has been made,
%
% c) if you make any additions, then change the name of the file, and
%
% d) you don't try to make any money out of this.
%
% See the Gnu manifesto for details on why software ought to be free.
%
% If you are worrying about the first three clauses, they're just
% there to make sure tons of different styles with the same name
% don't proliferate. If you want to remove a definition, then just
% comment it out (adding a %, not deleting anything).
%
% Tugboat are given permission to publish any or all of this.
%
% This style provides a pile of lambda-calculus and list-handling
% macros of an incredibly obtuse nature. Read Lambda.tex to find out
% what they all do and how they do it. This \TeX\ code was formally
% verified.
%
% Alan Jeffrey, 25 Jan 1990.
\def\Identity#1{#1}
\def\Error%
{\errmessage{Abandon verification all
ye who enter here}}
\def\First#1#2{#1}
\def\Second#1#2{#2}
\def\Compose#1#2#3{#1{#2{#3}}}
\def\Twiddle#1#2#3{#1{#3}{#2}}
\let\True=\First
\let\False=\Second
\let\Not=\Twiddle
\def\And#1#2{#1{#2}\False}
\def\Or#1#2{#1\True{#2}}
\def\Lift#1#2#3#4{#1{#4}{#2}{#3}{#4}}
\def\Lessthan#1#2{\TeXif{\ifnum#1<#2 }}
\def\gobblefalse\else\gobbletrue\fi#1#2%
{\fi#1}
\def\gobbletrue\fi#1#2%
{\fi#2}
\def\TeXif#1%
{#1\gobblefalse\else\gobbletrue\fi}
\def\Nil#1#2{#2}
\def\Cons#1#2#3#4{#3{#1}{#2}}
\def\Stream#1{\Cons{#1}{\Stream{#1}}}
\def\Singleton#1{\Cons{#1}\Nil}
\def\Head#1{#1\First\Error}
\def\Tail#1{#1\Second\Error}
\def\Foldl#1#2#3%
{#3{\Foldl@{#1}{#2}}{#2}}
\def\Foldl@#1#2#3#4%
{\Foldl{#1}{#1{#2}{#3}}{#4}}
\def\Foldr#1#2#3%
{#3{\Foldr@{#1}{#2}}{#2}}
\def\Foldr@#1#2#3#4%
{#1{#3}{\Foldr{#1}{#2}{#4}}}
\def\Cat#1#2{\Foldr\Cons{#2}{#1}}
\def\Reverse{\Foldl{\Twiddle\Cons}\Nil}
\def\All#1{\Foldr{\Compose\And{#1}}\True}
\def\Some#1{\Foldr{\Compose\Or{#1}}\False}
\def\Isempty{\All{\First\False}}
\def\Filter#1%
{\Foldr{\Lift{#1}\Cons\Second}\Nil}
\def\Map#1{\Foldr{\Compose\Cons{#1}}\Nil}
\def\Insert#1#2#3%
{#3{\Insert@{#1}{#2}}{\Singleton{#2}}}
\def\Insert@#1#2#3#4%
{#1{#2}{#3}%
{\Cons{#2}{\Cons{#3}{#4}}}%
{\Cons{#3}{\Insert{#1}{#2}{#4}}}}
\def\Insertsort#1{\Foldr{\Insert{#1}}\Nil}
\def\Unlistize#1{[#1\Unlistize@{}]}
\def\Unlistize@#1{#1\Foldr\Commaize{}}
\def\Commaize#1#2{, #1#2}
\def\Listize[#1]%
{\Listize@#1,\relax]}
\def\Listize@#1,#2]%
{\TeXif{\ifx\relax#2}%
{\Singleton{#1}}%
{\Cons{#1}{\Listize@#2]}}}
\def\Show#1[#2]%
{\Unlistize{#1{\Listize[#2]}}}
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