Re: How to implement lexical closures?

> [That sounds right, but it depends on the version of PL/I. I have
> the impenetrable 1976 PL/I standard and don't see anything about
> threads. -John]


When I worked at Pr1me, we had Freiberghouse's "full" PL/I compiler as
well as the subset G compiler. Neither had the concept of threads to
my knowledge, even the OS didn't. Instead Pr1me had a low cost
process exchange, comparable in cost to some threading context swaps,
IIRC save/restoring 4 to 8 registers could effect a process exchange.
A call instruction save/restored the same set. Thus, a procedure call
and a process exchange were essentially interchangeable.


I never used the IBM PL/I compilers, nor the Burrough's, VAX, or DG
ones. I did use the Multics one and don't remember threads there
either. However, my memory is that PL/I predates threading as a
significant concept. I recall threading being important on the DEC
Alpha, but that was in C.


Hope this helps,
-Chris


******************************************************************************
Chris Clark email: christopher.f.clark@compiler-resources.com
Compiler Resources, Inc. Web Site: http://world.std.com/~compres
23 Bailey Rd voice: (508) 435-5016
Berlin, MA 01503 USA twitter: @intel_chris
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[PL/I was developed at the same time as OS/360, and the threading in IBM
PL/I was basically the threading in OS/MVT. -John]

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