> I'm not sure why ((?:^(?:aaa|bbb|ccc))|(?:ddd|eee|ccc)) can be optimised but not (?:^aaa|ddd),

As I said:

Because "aaa" is a string of literal characters but "^aaa" isn't. "^" is a meta symbol for anchoring. The literal character is "\^", but that's not what you want.

If you need better explanation how trie works, please follow the links I provided.

The long answer

It certainly could be implemented for surrounding anchors too, just by using the workaround I showed.

But it's normally a bargain between code complexity and trade-off.

Perl's source is already suffering from covering too many edge cases which are only of interest for a small minority of users. And they shout the loudest when backwards compatibility is broken.

At the same time the code is getting increasingly complicated to maintain.

For instance: you could volunteer to implement a solution which creates multiple trie alterations surrounded by different anchors. (Not trivial to test)

Then someone with a commit bit has to decide if it's worth the resulting trouble to test and maintain that code in eternity.

In the end it's strategically easier to provide a CPAN module covering this edge case.

Usage would show if it's of wider interest or just pleasing you and a handful of others.

Cheers Rolf
(addicted to the Perl Programming Language :)
see Wikisyntax for the Monastery

In reply to Re^3: Alternations and anchors (trie optimization) by LanX
in thread Alternations and anchors by Chuma

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