lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4766) Pattern token filter which emits a token for every capturing group
Date Mon, 11 Feb 2013 14:41:13 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4766?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575813#comment-13575813
] 

Simon Willnauer commented on LUCENE-4766:
-----------------------------------------

I tend to disagree that this should be a tokenizer. IMO a tokenizer should only split tokens
in a stream fashion and should not emit tokens on the same position really. This is what token
filters should do. It also clashes with reuseability since you can't really reuse tokenizers
you have to decide which one you want. At some point you need to know what you are doing here
really. I don't have a definite answer but there is currently no clean way to do what clinton
wants to do IMO.
                
> Pattern token filter which emits a token for every capturing group
> ------------------------------------------------------------------
>
>                 Key: LUCENE-4766
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4766
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: modules/analysis
>    Affects Versions: 4.1
>            Reporter: Clinton Gormley
>            Assignee: Simon Willnauer
>            Priority: Minor
>              Labels: analysis, feature, lucene
>             Fix For: 4.2
>
>         Attachments: LUCENE-4766.patch, LUCENE-4766.patch
>
>
> The PatternTokenizer either functions by splitting on matches, or allows you to specify
a single capture group.  This is insufficient for my needs. Quite often I want to capture
multiple overlapping tokens in the same position.
> I've written a pattern token filter which accepts multiple patterns and emits tokens
for every capturing group that is matched in any pattern.
> Patterns are not anchored to the beginning and end of the string, so each pattern can
produce multiple matches.
> For instance a pattern like :
> {code}
>     "(([a-z]+)(\d*))"
> {code}
> when matched against: 
> {code}
>     "abc123def456"
> {code}
> would produce the tokens:
> {code}
>     abc123, abc, 123, def456, def, 456
> {code}
> Multiple patterns can be applied, eg these patterns could be used for camelCase analysis:
> {code}
>     "([A-Z]{2,})",
>     "(?<![A-Z])([A-Z][a-z]+)",
>     "(?:^|\\b|(?<=[0-9_])|(?<=[A-Z]{2}))([a-z]+)",
>     "([0-9]+)"
> {code}
> When matched against the string "letsPartyLIKEits1999_dude", they would produce the tokens:
> {code}
>     lets, Party, LIKE, its, 1999, dude
> {code}
> If no token is emitted, the original token is preserved. 
> If the preserveOriginal flag is true, it will output the full original token (ie "letsPartyLIKEits1999_dude")
in addition to any matching tokens (but in this case, if a matching token is identical to
the original, it will only emit one copy of the full token).
> Multiple patterns are required to allow overlapping captures, but also means that patterns
are less dense and easier to understand.
> This is my first Java code, so apologies if I'm doing something stupid.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message