The Importance of Terminology's Quality
John W Kennedy
jwkenne at attglobal.net
Wed Jul 2 03:56:58 CEST 2008
Robert Maas, http://tinyurl.com/uh3t wrote:
> Why this response is so belated:
> = <news:rem-2008jun25-003 at yahoo.com>
>> Date: Tue, 24 Jun 2008 18:42:15 -0400
>> From: John W Kennedy <jwke... at attglobal.net>
>> ... the "thunks" were necessary at the machine-language level to
>> /implement/ ALGOL 60, but they could not be expressed /in/ ALGOL.
> Ah, thanks for the clarification. Is that info in the appropriate
> WikiPedia page? If not, maybe you would edit it in?
It is explained s.v. "thunk", which is referenced from "ALGOL 60". The
ALGOL "pass-by-name" argument/parameter matching was perhaps the most
extreme example ever of a language feature that was "elegant" but
insane. What it meant, in effect, was that, unless otherwise marked,
every argument was passed as two closures, one that returned a fresh
evaluation of the expression given as the argument, which was called
every time the parameter was read, and one that set the argument to a
new value, which was called every time the parameter was set.
ALGOL 60 could not create generalized user-written closures, but could
create one no more complex than a single expression with no arguments of
its own simply by passing the expression as an argument. But it was not
thought of as a closure; that was just how ALGOL 60 did arguments.
John W. Kennedy
"Give up vows and dogmas, and fixed things, and you may grow like
That. ...you may come to think a blow bad, because it hurts, and not
because it humiliates. You may come to think murder wrong, because it
is violent, and not because it is unjust."
-- G. K. Chesterton. "The Ball and the Cross"
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