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Message-ID:  <4E95BEB8.4030803@nag.co.uk>
Date:         Wed, 12 Oct 2011 17:22:16 +0100
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From: David Carlisle <davidc@NAG.CO.UK>
Organization: NAG
Subject: Re: Church booleans
To: LATEX-L@listserv.uni-heidelberg.de
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Status: R

> These may look strange, but turn out to be two objects that are very
> familiar to us: \use_i:nn and \use_ii:nn respectively (or
> \@firstoftwo and \@secondoftwo, for those who still think in 2e terms
> (like me))


http://www.ctan.org/tex-archive/macros/plain/contrib/lambda


\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


:-)

David

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