On Fri, May 13, 2005 at 11:54:47AM -0500, Patrick R. Michaud wrote: : $r1 = rx / abc :: def | ghi :: jkl | mn :: op /; : $r2 = rx / abc ::: def | ghi ::: jkl | mn ::: op /; : $r3 = rx / [ abc :: def | ghi :: jkl | mn :: op ] /;
I would prefer that $r1 work like $r3, not like $r2, for two reasons. First, it gives a useful distinction of meaning. Second, and more importantly, outer lexical scopes are often delimited by something other than what the inner scopes are delimited by. A file scope or an eval string is no less a block because it's not delimited by curlies. In the same way, the outer delimiters of an rx/.../ should function as if you'd said rx/[...]/. : However, *if* we say that :: at the top level fails the rule, that : means that as things currently stand : : $z1 = rx :w /foo/; : $z2 = rx /:w::foo/; : $z3 = rx /[:w::foo]/; : : can be a little surprising: : : "hello foo" ~~ $z1 # matches "foo" : "hello foo" ~~ $z2 # fails immediately upon the 'h' != 'f' : "hello foo" ~~ $z3 # matches "foo" : : which was the point of my original post. And that's the third reason. A :: at the beginning of a "group" should essentially be a no-op. By the way, I still think of it as "a group of alternatives" even if there's only one alternative, and no |. But I can see how that can be misread to imply at least two alternatives. (We're also hampered by the linguistic fact that "alternative" can mean either how many choices you have to make or how many paths are open to you. In other words, one alternative of the first sort presents you two alternatives of the second sort. And if there's no alternative, you only have one alternative. Ain't English wonderful? Anyway, :: fails the current lexical scope, not the current rule. ::: fails the current rule in a more dynamically scoped way, which is why it also fails the engine applying the implicit .*?. And of course, failure to <commit> is almost completely dynamic in scoping. It's more like unwinding an exception till you find a handler that knows it's the outer rule. Larry
