[plt-scheme] Re: to define, or to let (last try)

From: Bill Richter (richter at math.northwestern.edu)
Date: Wed Apr 28 23:42:41 EDT 2004

   Matthias Felleisen <matthias at ccs.neu.edu> responded to me: 

   As you all know, PLT Scheme has a fix evaluation order. We believe
   it is the correct thing to do and until we see further evidence, we
   stick with it. Evidence will *not* come with theoretical arguments.
   It will have to come in new practical arguments. And believe it or
   not: Matthew and I and everyone else of core PLT has seen a lot of
   arguments and evidence on this topic. You will have to think hard
   to create new evidence.

   P.S. Good enough for a pronouncement?

That's great, Matthias, but you're a top theoreticians.  Can you make
a theoretical pronouncement about these 3 issues, and then we'll quit:

1) Definite semantics is important for reasoning about programs.

2) Sequential programming style is so bad that we want unenforceable
constructions indicating coder's belief in eval order independence.

3) Depending on Mzscheme's left->right eval order creates a problem
which didn't exist in non-buggy ambiguous eval order R5RS programs:

(.... EXP ...) isn't equivalent to (let ([x EXP]) (... x ... ))

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