[Haskell-cafe] Re: Data constructors versus types

[Anton van Straaten]

jerzy.karczmarczuk at info.unicaen.fr wrote:
>  [McCarthy's] aim was to use the mathematical
>  formalismus as languages and not as calculi. This is the root of
>  the historical fact that he never took the Lambda-Calculus conversion
>  rules as a sound basis for LISP implementation."
> So, I believe it is not so briliant an idea to confound the Church calculus
> with Lisp!

It's difficult to extricate the two, as Lisp & McCarthy's experience 
shows.  The decision to use lambda notation without the accompanying 
semantics would have been fine if Lisp had not also had first-class 
functions.  But with first-class functions, and without lexical scoping 
semantics, Lisp suffered from scoping bugs which were only resolved once 
Lisp's 'lambda' was changed to follow Church's semantics, as Sussman and 
Steele originally did for Scheme.

When CL adopted lexical scoping, it was seen as a choice, but it wasn't 
really much of a choice.  The choice was between continuing with a 
fundamentally buggy language and working around those bugs somehow, or 
fixing it by adopting Church's lexical scoping rules.

> Wherever you look, you find plenty of occasions to
> err, it suffices to put yourself in a mode of a dead person from the
> movie "The sixth sense" of M. Night Shyamalan, with Bruce Willis, and
> Haley Joel Osment. 

I see dead languages...

Anton