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From: philip@pescadero.Stanford.EDU (Philip Machanick)
Newsgroups: comp.lang.misc
Subject: Re: Algol, and language design
Message-ID: <1990Jul26.171822.7193@Neon.Stanford.EDU>
Date: 26 Jul 90 17:18:22 GMT
References: <2406@l.cc.purdue.edu> <25630@cs.yale.edu> <58091@lanl.gov> <1990Jul26.024449.1777@esegue.segue.boston.ma.us>
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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:
> > How about nested scopes and recursion?  I find them handy from time
to time.
> 
> Nested scopes of DO loops are present in Fortran.  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?
"Nested scopes" refers to the ability to define local names within one
compilation unit. DO loops do not introduce "scope". Recursion is a
problem if an architecture doesn't have a built in stack - not an issue
on modern architectures. Why? Because language design required an efficient
stack. Other more esoteric mechanisms like hardware displays to access
non-local variables haven't paid off as much, and so are not in common
use. "globals in registers across recursion"? How many _compilers_ manage
registers across _any_ procedure calls? (Just asking.)

Philip Machanick
philip@pescadero.stanford.edu