🚀 go-pugleaf

preston@titan.rice.edu (Preston Briggs) wrote:

> So, I dunno about Lisp vs. Algol.  We can settle and say that
> Church invented nested scopes as part of the lambda calculus.

You get them in the predicate calculus too.  So they must date back to
Frege's "Begriffschrift" of around 1879.  Maybe a bit of digging could
unearth a similar analysis of names in mediaeval Arabic or Scholastic
logic.

In fact the nearest thing visually to an Algol block-structured program is
a Fitch natural deduction proof for predicate logic (the "flags" introduced
on subproofs for E-elimination or A-introduction are local variables with
lexical scoping).  These were presented in Fitch's elementary logic
textbook of the early 50s; he must have invented the notation over ten
years before that.  In fact the similarity to Algol is so close I can't
believe the Algol committee thought the idea up independently.

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