>>>>> "DAP" == Deborah Ariel Pickett <[EMAIL PROTECTED]> writes:
DAP> C<rule> allows us to define both named and anonymous rules, depending on
DAP> context. C<rx> allows us to define only anonymous rules. C<rule> is
DAP> the more general one, and you can use it exclusively if that's what you
DAP> feel like.
DAP> The only extra piece of syntactic sugar that C<rx> is giving us over
DAP> C<rule>[*] is the ability to have arbitrary delimiters. If I were
DAP> satisfied with always using C<{}> as delimiters for C<rx> then a
DAP> program would run the same if I did a C<s:each/rx/rule/> on it.
not in one case. if you had named rules then you couldn't do that
substition as rx// has no syntax for a name. i assume you could use the
:= op to alias an rx to a name and that should be the same as a named
rule.
DAP> Now . . .
DAP> Is there some _syntactic_ constraint (i.e., required by the parser)
DAP> that requires C<rule> to use braces for delimiters? That is, shouldn't
DAP> the following:
DAP> $config_line = rule ($ident) { <$ident> = \N* }
DAP> always be parseable for any given value of C<{> and C<}> (barring
DAP> obvious exceptions like colons and parentheses)?
no, rules are like subs there and only {} are allowed.
DAP> Or, to put it more succinctly: do there exist two pieces of
DAP> *syntactically correct* code like
DAP> ... rule ...
DAP> and
DAP> ... rx ...
DAP> (where the ... are identical in both) which each produce *valid* and
DAP> *different* semantics?
not that i can see. they are just syntactic variants with some slight
differences (naming vs delimiters).
DAP> To me, that'd be the only reason for C<rx> and C<rule> to be
DAP> different keywords. [**] Especially since we're making such a big
DAP> deal about patterns and subroutines having lots of parallels.
DAP> The same parallel doesn't exist for subroutines[***]; why should
DAP> it for pattern matching?
rx// is closer to how qr// works and looks in perl 5. so if you just
want to create a anon regex, then this would look familiar
$re = rx/ blah / ; # whitespace always allowed now
rule could be used there but it is longer and not similar to perl5
$re = rule { blah } ;
DAP> [**] As opposed to C<rx> and C<rule> being two different spellings of
DAP> the same keyword, something I don't object to.
they aren't different spellings. they have different syntax but the same
semantics.
uri
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Uri Guttman ------ [EMAIL PROTECTED] -------- http://www.stemsystems.com
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