From: "Paul Gilmartin" <00000014e0e4a59b-dmarc-requ...@listserv.uga.edu>
Sent: Saturday, February 17, 2018 1:27 PM
On 2018-02-16, at 18:45:04, Robin Vowels wrote:
From: "Paul Gilmartin"
Sent: Saturday, February 17, 2018 6:18 AM
On 2018-02-16, at 11:33:05, Bernd Oppolzer wrote:
IMO, Niklaus Wirth ... came to this decision,
to allow numbers as labels only, and to force them to be declared before using
them.
The prior declaration is (almost) necessary for single-pass compilation.
No it isn't.
XPL is a single-pass compiler, and declaration of identifiers
is not required.
I said "almost".
"Almost" was in parentheses.
Whether almost necessary or necessary, it is not true.
Declarations of labels are not required.
You can keep a lookback list of addresses to be
plugged when they can be resolved. At some point this becomes
tantamount to a second pass, over internal text.
It isn't tantamount to a second pass.
Does XPL have nested procedure declarations, which complicate
the chore?
Yes, it has nested procedures. XPL is a small dialect of PL/I.
C function prototypes, not required by K&R, embody some of the
prior declaration facility.
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