[plt-scheme] Why "lambda"?

From: hendrik at topoi.pooq.com (hendrik at topoi.pooq.com)
Date: Tue May 26 14:09:01 EDT 2009

On Tue, May 26, 2009 at 11:09:57AM -0400, Matthias Felleisen wrote:
> The story is that in the 10s and 20s, mathematicians and logicians  
> used ^ as a notation for set abstraction, as in ^i : i is prime.  
> Church used ^` (i.e., a primed version of this symbol) for function  
> abstraction, because functions are just sets with extra properties.  
> The first type setter/secretary read it as λ and Church was fine  
> with. True or not? I don't know but it's fun.

I heard a version of this story, with a few more details, from John 
Seldin, who had heard it from Curry directly.

Originally, Curry had wanted a giant roof over the entire 
lambda-expression, from the binding occurrence of the variable all the 
way to the end (so it would functino as a kind of bracket), but since 
this was too expensive to type-set, he settled on a circumflex accent 
over the variable.

Then it turned out the typesetter couldn't handle circumflex accents 
over arbitrary characters, so it moved around and becamd a lambda.

-- hendrik

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