Proposal: new UnicodeSet constructor, applyPattern

Jitterbug 3262
http://www.jtcsv.com/cgibin/icu-bugs/others?id=3262

Expires: Oct 21 2003

I've added two new API to UnicodeSet:

    /**
     * Constructs a set from the given pattern.  See the class description
     * for the syntax of the pattern language.
     * @param pattern a string specifying what characters are in the set
     * @param pos on input, the position in pattern at which to start 
parsing.
     * On output, the position after the last character parsed.
     * @param options bitmask for options to apply to the pattern.
     * Valid options are USET_IGNORE_SPACE and USET_CASE_INSENSITIVE.
     * @param symbols a symbol table mapping variable names to values
     * and stand-in characters to UnicodeSets; may be NULL
     * @param status input-output error code
     * @draft ICU 2.8
     */
    UnicodeSet(const UnicodeString& pattern, ParsePosition& pos,
               uint32_t options,
               const SymbolTable* symbols,
               UErrorCode& status);

    /**
     * Parses the given pattern, starting at the given position.  The
     * character at pattern.charAt(pos.getIndex()) must be '[', or the
     * parse fails.  Parsing continues until the corresponding closing
     * ']'.  If a syntax error is encountered between the opening and
     * closing brace, the parse fails.  Upon return from a successful
     * parse, the ParsePosition is updated to point to the character
     * following the closing ']', and a StringBuffer containing a
     * pairs list for the parsed pattern is returned.  This method calls
     * itself recursively to parse embedded subpatterns.
     *
     * @param pattern the string containing the pattern to be parsed.
     * The portion of the string from pos.getIndex(), which must be a
     * '[', to the corresponding closing ']', is parsed.
     * @param pos upon entry, the position at which to being parsing.
     * The character at pattern.charAt(pos.getIndex()) must be a '['.
     * Upon return from a successful parse, pos.getIndex() is either
     * the character after the closing ']' of the parsed pattern, or
     * pattern.length() if the closing ']' is the last character of
     * the pattern string.
     * @param options bitmask for options to apply to the pattern.
     * Valid options are USET_IGNORE_SPACE and USET_CASE_INSENSITIVE.
     * @param symbols a symbol table mapping variable names to
     * values and stand-ins to UnicodeSets; may be NULL
     * @return a reference to this
     * @draft ICU 2.8
     */
    UnicodeSet& applyPattern(const UnicodeString& pattern,
                             ParsePosition& pos,
                             uint32_t options,
                             const SymbolTable* symbols,
                             UErrorCode& status);

These API expose previously "hidden" functionality of UnicodeSet:
1. The ability to parse part of a string (ParsePosition).
2. The ability to specify control options for white space and case 
sensitivity (and other options in the future).
3. The ability to pass in a SymbolTable to control variable dereferencing 
and stand-in expansion to nested UnicodeSets.

Please send comments to this mailing list.

Alan Liu
IBM GCoC - San Jose