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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2167) StandardTokenizer Javadoc does not correctly describe tokenization around punctuation characters
Date Wed, 24 Feb 2010 23:15:28 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838073#action_12838073
] 

Robert Muir commented on LUCENE-2167:
-------------------------------------

btw, here is some statement that seems to confirm my suspicions, from the standard:

In section 6.3, there is an example of the grapheme cluster boundaries converted into a simple
regex (the kind we could do easily in jflex now that it has the properties available).

They make this statement: Such a regular expression can also be turned into a fast, deterministic
finite-state machine. Similar regular expressions are possible for Word boundaries. Line and
Sentence boundaries are more complicated, and more difficult to represent with regular expressions.

> StandardTokenizer Javadoc does not correctly describe tokenization around punctuation
characters
> ------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-2167
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2167
>             Project: Lucene - Java
>          Issue Type: Bug
>    Affects Versions: 2.4.1, 2.9, 2.9.1, 3.0
>            Reporter: Shyamal Prasad
>            Priority: Minor
>         Attachments: LUCENE-2167.patch, LUCENE-2167.patch
>
>   Original Estimate: 0.5h
>  Remaining Estimate: 0.5h
>
> The Javadoc for StandardTokenizer states:
> {quote}
> Splits words at punctuation characters, removing punctuation. 
> However, a dot that's not followed by whitespace is considered part of a token.
> Splits words at hyphens, unless there's a number in the token, in which case the whole

> token is interpreted as a product number and is not split.
> {quote}
> This is not accurate. The actual JFlex implementation treats hyphens interchangeably
with
> punctuation. So, for example "video,mp4,test" results in a *single* token and not three
tokens
> as the documentation would suggest.
> Additionally, the documentation suggests that "video-mp4-test-again" would become a single
> token, but in reality it results in two tokens: "video-mp4-test" and "again".
> IMHO the parser implementation is fine as is since it is hard to keep everyone happy,
but it is probably
> worth cleaning up the documentation string. 
> The patch included here updates the documentation string and adds a few test cases to
confirm the cases described above.

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