Re: language design implications for variant records in a pascal-like language

glen herrmannsfeldt <gah@ugcs.caltech.edu> writes:


> Part of the design of PL/I was that you wouldn't have to learn all of
> it to use it.


A worthy goal.


>...That was used as the reason for not having reserved
> words. (You have to at least know the word to know not to use it.)


I don't see that. I mean, you don't actually have to memorize the
list of reserved words. You get an error message, saying you used a
reserved word as an identifier, so you fix it and recompile. After a
while, you've memorized all the reserved words you're likely to use
incorrectly. Failure to know some obscure reserved word won't cause a
(run-time) bug.


At least, that's true if the compiler gives good error messages about
obscure reserved words. "Reserved word 'until' used as an
identifier.", as opposed to "Compiler saw 'until', and is now
hopelessly confused...<cascade of junk messages>". That requires the
language syntax to make such good error messages feasible -- which is
more-or-less the same sort of syntax that can allow a
reserved-word-free syntax.


> Also, the huge list of reserved words for COBOL may have been on the
> mind of PL/I designers.


Sounds likely. In other words, "COBOL has too many reserved words,
therefore reserved words are evil, therefore let's eliminate reserved
words." Overreaction?


- Bob
[Back when PL/I was designed, "recompile" meant resubmitting a deck of
cards and potentially waiting several hours. To avoid that problem,
COBOL programmers did wacky things like starting all variable names
with a digit, just to avoid the reserved words. These days I agree,
reserved words are less of a big deal, but modern languages don't have
400 reserved works like COBOL does. -John]

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