Re: Regular Expressions Proposal

Good point. Something we ought to have at some point is the ability to have a
mode in the regular expression to use either a locale, or be locale-neutral.
Like the other modes, this should allow turning on or off during different parts
of the expression. The locale could be settable on the regular expression
object -- so it is not just the default locale.

However, this is not scheduled for 2.8.

Mark
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----- Original Message ----- 
From: "George Rhoten" <[email protected]>
To: <[email protected]>
Sent: Wed, 2003 Oct 22 17:51
Subject: Re: Regular Expressions Proposal


> When dealing with word boundaries, is it going to be Unicode default
> behavior or will it be locale sensitive?
>
> George Rhoten
> IBM Globalization Center of Competency/ICU  San José, CA, USA
>
>
>
>
> Andy Heninger <[email protected]>
> Sent by: [email protected]
> 10/22/2003 03:41 PM
> Please respond to Andy Heninger
>
>         To:     [email protected]
>         cc:
>         Subject:        Regular Expressions Proposal
>
>
> This is a proposal for enhancement of the ICU Regular Expression
> package, to address a few things that have come up with usage so far.
>
> 1.  Add new API
> UBool RegexMatcher::lookingAt(int32_t stringIndex,
> UErrorCode &status);
>
> UBool RegexMatcher::matches(int32_t stringIndex,
> UErrorCode &status);
>
> These would function like the already existing lookingAt() and
> matcthes() methods, but would check for a match starting at
> the specified position.  The existing methods start at the
> current position, which is either the start, or, with repeated
> calls, the position following the previous match.
>
>
> 2.  Add new API
> RegexMatcher &reset(int32_t stringIndex,
> UErrorCode &status)
>
> Removes any memory of previous matches, and sets the current
> position of the RegexMatcher, causing subsequent find()
> or matches() operations to begin at the specified position.
>
> Report an error if the string index is out of bounds.
>
> The existing reset() function sets the current position to
> the beginning of the input string.
>
> 2.  Add an option for word boundaries ( \b in regex patterns) to
> be determined according to the rules from Unicode UAX 29.
> The current implementation is based on Perl's word boundaries,
> and this (Perl conventions) would remain the default.
>
> Unicode word boundaries mode will be selected by means of an
> option flag.
>
> To the enum of option flags in file regex.h, add
> UREGEX_UWORD
>
> To the list of flags that can be used within a pattern, add 'w'.
> The existing flags are 'ismx', so the set of flags becomes 'ismwx'
>
> Examples:
>
> "(?iw)[aeiou].*?\b"   A pattern to match any word beginning with
> a vowel [aeiou], with the flags
> i  (case insensitive) and
> w  (Unicode style word boundaries).
>
> ---
>
>
> // Initialize a matcher object from a pattern in a string,
> //   with the default word match mode set to
> //   Unicode word boundaries.
> RegexMatcher myMatcher(patternString, UREGEX_UWORD, status);
>
>
> 3.  Add new API
> UBool  RegexMatcher::touchedEnd();
>
> Return true if the most recent attempted match or match touched the
> end of the input string.  For failed matches, this normally
> means that some amount of additional input, appended to the
> existing input string, could have resulted in a match.  (Note
> that there are some degenerate cases involving look-around
> operations where this is not true, but these generally involve
> non-sensical patterns.)
>
> The intent of this function is to allow a determination of
> potential matches to be made while input text is incrementally
> received.
>
> These additions to ICU regular expressions are scheduled for ICU 2.8.
> Any comments would be most appreciated.
>
> -- Andy Heninger
> [email protected]
>
>
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