🚀 go-pugleaf

In article <8903032139.AA00466@gilroy.pa.dec.com> Modula2 List <INFO-M2%UCF1VM.bitnet@jade.berkeley.edu> writes:
>
>INC(CARDINAL(code), 1);
>
>is not accepted by most Modula-2 compilers, because ``CARDINAL(code)'' is an
>expression (an r-value, for those conversant with C's description) rather than
>a variable (an l-value).  INC effectively takes a VAR parameter, so insists
>upon having a variable.
>
>I don't consider the cast to really be an expression.  I see it as a type
>conversion which is more properly seen as a viewpoint change rather than a
>computation.  I therefore consider this a silly restriction, and done
>something about it in the Modula-2 compiler I maintain.  But it certainly
>isn't standard.
>
> Joel McCormack

*Syntactically*, "CARDINAL(BITSET{2,5})" is an expression.  The only way
to differentiate between this and any other expression is by means of
the semantics.  If the parser permits expressions everywhere that
"idents" and/or "qualidents" are allowed, then it must rely on the
semantic analyzer to distinguish between legal and illegal expression
usage.  But Wirth published a grammar for Modula-2 that explicitly
outlawed the usage of what are syntactically expressions in cases
like the one above.  So any compiler that relaxes this restriction
is not standard.  The fact that the resulting language may be an improvement
over the one defined by Wirth has not been enough to motivate most
compiler writers, whose work so far is largely a labor of love.

The international standardization effort is the last great hope for
addressing this issue.  From what I have heard, I wouldn't expect
any changes that would allow "INC(CARDINAL(x), 1)" anytime soon,
unfortunately.

If you want to complain about the shortcomings of M2, start with the
fact that modules are not classes, and don't forget to mention the
lack of an inheritance mechanism and parametric types/modules.

-- 
Alan Lovejoy; alan@pdn; 813-530-2211; ATT-Paradyne: 8550 Ulmerton, Largo, FL.
Disclaimer: I do not speak for ATT-Paradyne.  They do not speak for me. 
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