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From: brian@comp.vuw.ac.nz (Brian Boutel)
Newsgroups: comp.lang.functional
Subject: Re: why lambda ?
Message-ID: <1991Feb25.003516.6040@comp.vuw.ac.nz>
Date: 25 Feb 91 00:35:16 GMT
References: <1952@seti.inria.fr> <12733@darkstar.ucsc.edu>
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In article <12733@darkstar.ucsc.edu>, kjell@saturn.ucsc.edu (Kjell Post)
writes:
|> In article <1952@seti.inria.fr> ddr@margaux.inria.fr (Daniel de
|> Rauglaudre) writes:
|> >There is a question of great importance in our institute: why
|> "lambda"
|> >in "lambda calculus" ? Why not "alpha" or "dzeta" or any other
|> symbol ?
|> >Does anybody know the origin of this choice ? Thank you for you
|> answers.
|> >
|> >	Daniel de Rauglaudre
|> >	INRIA - France
|> >	ddr@inria.inria.fr
|> 
|> 
|> You could ask Church (I think he's still alive) but I don't think
|> that
|> will help you because the last time they asked him he didn't
|> remember
|> why he picked lambda. 
|> 
|> There are some speculations on lambda being a degenerate form of the
|> caret-sign (``^'') but I recall Church saying that "it's possible
|> but
|> I don't know...".  

I read somewhere (and I would like to be reminded where) that the origin
is connected with the carat-sign.

In, I think, Whitehead and Russell's Principia Mathematica, the carat is
used to mark each occurance of a bound variable in an expression. Later,
the usage got changed to mark each bound variable once only, by
prefixing the expression with a big caret and the name of the bound
variable.  The big caret is like a capital lambda /\. Later still, (for
printer's convenience?) the lambda became lower case.

--brian

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