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From: art@cs.bu.edu (Al Thompson)
Newsgroups: comp.lang.misc
Subject: Re: Algol, and language design
Message-ID: <61396@bu.edu.bu.edu>
Date: 26 Jul 90 17:01:43 GMT
References: <25630@cs.yale.edu> <58091@lanl.gov> <1990Jul26.024449.1777@esegue.segue.boston.ma.us> <2406@l.cc.purdue.edu>
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Organization: Computer Science Department, Boston University, Boston, MA, USA
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In article <2406@l.cc.purdue.edu> cik@l.cc.purdue.edu (Herman Rubin) writes:
|In article <1990Jul26.024449.1777@esegue.segue.boston.ma.us>, johnl@esegue.segue.boston.ma.us (John R. Levine) writes:
|> In article <58091@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
[...]
|> 
|> How about nested scopes and recursion?  I find them handy from time to time.
|
|Nested scopes of DO loops are present in Fortran.

Scope, as in the sense of variables visible only from within the loop?  Is
this what you meant?  Algol had a feature in which local data could be
declared local to any begin end pair.  Thus the compound statement in
Algol would resemble a procedure except it had no parameters and could not
be called elsewhere.

  Mathematicians have used
|recursion for ages, and the problems with implementing recursion in the
|architecture of the time were horrendous.  Frankly, some of them still are.
|What language allows carrying globals in registers across recursion?

How is carrying globals in registers across recursion a language issue?
It's an implementation issue.  Whether you can do it or not is a function
of the cleverness of the compiler writer and the architecture upon which
it is implemented.

|
|One of the things which should be noted was that, at the time, registers
|were few and transfer and memory access were relatively fast compared with
|computation.

The world's first commercial Algol machine (the Burroghs B5000 and
derivatives) didn't have any registers, at least none visible to the user.