Reimplementing ToUpper()

Question

How would you write ToUpper() if it didn't exist? Bonus points for i18n and L10n

Curiosity sparked by this: http://thedailywtf.com/Articles/The-Long-Way-toUpper.aspx

Answer 1

I dont think SO can handle the size of the unicode tables in a single posting :)

Unfortunately, it is not so easy as just char.ToUpper() every character.

Example:

(string-upcase "Straße")    ⇒ "STRASSE"
(string-downcase "Straße")  ⇒ "straße"
(string-upcase "ΧΑΟΣ")      ⇒ "ΧΑΟΣ"
(string-downcase "ΧΑΟΣ")    ⇒ "χαος"
(string-downcase "ΧΑΟΣΣ")   ⇒ "χαοσς"
(string-downcase "ΧΑΟΣ Σ")  ⇒ "χαος σ"
(string-upcase "χαος")      ⇒ "ΧΑΟΣ"
(string-upcase "χαοσ")      ⇒ "ΧΑΟΣ"

Answer 2

1. I download the Unicode tables
2. I import the tables into a database
3. I write a method upper().

Here is a sample implementation ;)

public static String upper(String s) {
    if (s == null) {
        return null;
    }

    final int N = s.length(); // Mind the optimization!
    PreparedStatement stmtName = null;
    PreparedStatement stmtSmall = null;
    ResultSet rsName = null;
    ResultSet rsSmall = null;
    StringBuilder buffer = new StringBuilder (N); // Much faster than StringBuffer!
    try {
        conn = DBFactory.getConnection();
        stmtName = conn.prepareStatement("select name from unicode.chart where codepoint = ?");
        // TODO Optimization: Maybe move this in the if() so we don't create this
        // unless there are uppercase characters in the string.
        stmtSmall = conn.prepareStatement("select codepoint from unicode.chart where name = ?");
        for (int i=0; i<N; i++) {
            int c = s.charAt(i);
            stmtName.setInt(1, c);
            rsName = stmtName.execute();
            if (rsName.next()) {
                String name = rsName.getString(1);
                if (name.contains(" SMALL ")) {
                    name = name.replaceAll(" SMALL ", " CAPITAL ");

                    stmtSmall.setString(1, name);
                    rsSmall = stmtSmall.execute();
                    if (rsSmall.next()) {
                        c = rsSmall.getInt(1);
                    }

                    rsSmall = DBUtil.close(rsSmall);
                }
            }
            rsName = DBUtil.close(rsName);
        }
    }
    finally {
        // Always clean up
        rsSmall = DBUtil.close(rsSmall);
        rsName = DBUtil.close(rsName);
        stmtSmall = DBUtil.close(stmtSmall);
        stmtName = DBUtil.close(stmtName);
    }

    // TODO Optimization: Maybe read the table once into RAM at the start
    // Would waste a lot of memory, though :/
    return buffer.toString();
}

;)

Note: The unicode charts which you can find on unicode.org contain the name of the character/code point. This string will contain " SMALL " for characters which are uppercase (mind the blanks or it might match "SMALLER" and the like). Now, you can search for a similar name with "SMALL" replaced with "CAPITAL". If you find it, you've found the captial version.

Answer 3

I won't win the bonus points, but here it is for 7-bit ASCII:

char toupper(char c)
{
    if ((c < 'a') || (c > 'z')) { return c; }
    else { return c & 0xdf; }
}

Answer 4

No static table is going to be sufficient because you need to know the language before you know the correct transforms.

e.g. In Turkish i needs to go to İ (U+0130) whereas in any other language is needs to go to I (U+0049) . And the i is the same character U+0069.

Answer 5

Let me suggest even more bonus points for languages such as Hebrew, Arabic, Georgian and others that just do not have capital (upper case) letters. :-)

Answer 6

in python ..

touppe_map = { massive dictionary to handle all cases in all languages }
def to_upper( c ):
   return toupper_map.get( c, c )

or, if you want to do it the "wrong way"

def to_upper( c ):
  for k,v in toupper_map.items():
     if k == c: return v
  return c