Yes, both of those work, and arguably they're a little cleaner
looking than my conjunction approach-- though it's not necessarily any
easier to think about. It looks like a pattern that's matching
for three things in order, but the zero-widthness of the "before"
let's them all work on top of each other.
I keep thinking there's an edge case in these before/after tricks that
might matter if we weren't matching the one-word-per-line format of
the unix dictionaries, but I need to think about that a little more...
Peter Pentchev <r...@ringlet.net> wrote:
> On Fri, May 15, 2020 at 07:32:50PM -0700, Joseph Brenner wrote:
>> Regex engines by their nature care a lot about order, but I
>> occasionally want to relax that to match for multiple
>> multicharacter subpatterns where the order of them doesn't
>> matter.
>>
>> Frequently the simplest thing to do is just to just do multiple
>> matches. Let's say you're looking for words that have a "qu" a
>> "th" and also, say an "ea". This works:
>>
>> my $DICT = "/usr/share/dict/american-english";
>> my @hits = $DICT.IO.open( :r
>> ).lines.grep({/qu/}).grep({/th/}).grep({/ea/});
>> say @hits;
>> # [bequeath bequeathed bequeathing bequeaths earthquake earthquake's
>> earthquakes]
>
> Would something like this work for you?
>
> /^ <?before .* "qu" > <?before .* "th" > <?before .* "ea" > /
>
>> Where things get interesting is when you want a negated match of
>> one of the subpatterns. One of the things I like about the first
>> approach using multiple chained greps is that it's easy to do a
>> reverse match. What if you want words with "qu" and "th" but
>> want to *skip* ones with an "ea"?
>>
>> my @hits = $DICT.IO.open( :r
>> ).lines.grep({/qu/}).grep({/th/}).grep({!/ea/});
>> # [Asquith discotheque discotheque's discotheques quoth]
>
> Maybe something like this? (note the "!" instead of "?")
>
> /^ <?before .* "qu" > <?before .* "th" > <!before .* "ea" > /
>
> G'luck,
> Peter
>
> --
> Peter Pentchev r...@ringlet.net r...@debian.org p...@storpool.com
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>
