Allen's lambda syntax proposal

Dave Herman dherman at ccs.neu.edu
Sun Dec 21 05:09:03 PST 2008


> "^" also has a slight resemblance to the greek lambda, which is the  
> reason Haskell uses "\".

As an aside, the circumflex is actually the precursor to lambda:

"We end this introduction by telling what seems to be the story how  
the letter 'λ' was chosen to denote function abstraction. In Principia  
Mathematica the notation for the function f with f(x) = 2x + 1 is

      ^
     2x + 1.

Church originally intended to use the notation

     ^
     x.2x+1.

The typesetter could not position the hat on top of the x and placed  
it in front of it, resulting in
^x.2x + 1. Then another typesetter changed it into λx.2x + 1."

-- H. Barendregt, The Impact of the Lambda Calculus In Logic and  
Computer Science [1]

Dave

[1] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.26.7908



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