--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/luan/modules/StringLuan.java	Fri Aug 26 14:36:40 2016 -0600
@@ -0,0 +1,247 @@
+package luan.modules;
+
+import java.util.Arrays;
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+import luan.Luan;
+import luan.LuanState;
+import luan.LuanTable;
+import luan.LuanFunction;
+import luan.LuanException;
+import luan.LuanMethod;
+
+
+public final class StringLuan {
+
+	static int start(String s,int i) {
+		int len = s.length();
+		return i==0 ? 0 : i > 0 ? Math.min(i-1,len) : Math.max(len+i,0);
+	}
+
+	static int start(String s,Integer i,int dflt) {
+		return i==null ? dflt : start(s,i);
+	}
+
+	static int end(String s,int i) {
+		int len = s.length();
+		return i==0 ? 0 : i > 0 ? Math.min(i,len) : Math.max(len+i+1,0);
+	}
+
+	static int end(String s,Integer i,int dflt) {
+		return i==null ? dflt : end(s,i);
+	}
+
+	@LuanMethod public static Integer[] unicode(String s,Integer i,Integer j) throws LuanException {
+		Utils.checkNotNull(s);
+		int start = start(s,i,1);
+		int end = end(s,j,start+1);
+		Integer[] chars = new Integer[end-start];
+		for( int k=0; k<chars.length; k++ ) {
+			chars[k] = (int)s.charAt(start+k);
+		}
+		return chars;
+	}
+
+	public static String char_(int... chars) {
+		char[] a = new char[chars.length];
+		for( int i=0; i<chars.length; i++ ) {
+			a[i] = (char)chars[i];
+		}
+		return new String(a);
+	}
+
+	@LuanMethod public static byte[] to_binary(String s) {
+		return s.getBytes();
+	}
+
+	public static String lower(String s) throws LuanException {
+		Utils.checkNotNull(s);
+		return s.toLowerCase();
+	}
+
+	public static String upper(String s) throws LuanException {
+		Utils.checkNotNull(s);
+		return s.toUpperCase();
+	}
+
+	public static String trim(String s) throws LuanException {
+		Utils.checkNotNull(s);
+		return s.trim();
+	}
+
+	public static String reverse(String s) throws LuanException {
+		Utils.checkNotNull(s);
+		return new StringBuilder(s).reverse().toString();
+	}
+
+	public static String rep(String s,int n,String sep) {
+		if( n < 1 )
+			return "";
+		StringBuilder buf = new StringBuilder(s);
+		while( --n > 0 ) {
+			if( sep != null )
+				buf.append(sep);
+			buf.append(s);
+		}
+		return buf.toString();
+	}
+
+	public static String sub(String s,int i,Integer j) throws LuanException {
+		Utils.checkNotNull(s);
+		int start = start(s,i);
+		int end = end(s,j,s.length());
+		return s.substring(start,end);
+	}
+
+	@LuanMethod public static Object[] find(String s,String pattern,Integer init,Boolean plain) {
+		int start = start(s,init,0);
+		if( Boolean.TRUE.equals(plain) ) {
+			int i = s.indexOf(pattern,start);
+			return i == -1 ? null : new Integer[]{i+1,i+pattern.length()};
+		}
+		Matcher m = Pattern.compile(pattern).matcher(s);
+		if( !m.find(start) )
+			return null;
+		int n = m.groupCount();
+		Object[] rtn = new Object[2+n];
+		rtn[0] = m.start() + 1;
+		rtn[1] = m.end();
+		for( int i=0; i<n; i++ ) {
+			rtn[2+i] = m.group(i+1);
+		}
+		return rtn;
+	}
+
+	@LuanMethod public static String[] match(String s,String pattern,Integer init) {
+		int start = start(s,init,0);
+		Matcher m = Pattern.compile(pattern).matcher(s);
+		if( !m.find(start) )
+			return null;
+		int n = m.groupCount();
+		if( n == 0 )
+			return new String[]{m.group()};
+		String[] rtn = new String[n];
+		for( int i=0; i<n; i++ ) {
+			rtn[i] = m.group(i+1);
+		}
+		return rtn;
+	}
+
+	public static LuanFunction gmatch(String s,String pattern) throws LuanException {
+		Utils.checkNotNull(s);
+		final Matcher m = Pattern.compile(pattern).matcher(s);
+		return new LuanFunction() {
+			@Override public Object call(LuanState luan,Object[] args) {
+				if( !m.find() )
+					return null;
+				final int n = m.groupCount();
+				if( n == 0 )
+					return m.group();
+				String[] rtn = new String[n];
+				for( int i=0; i<n; i++ ) {
+					rtn[i] = m.group(i+1);
+				}
+				return rtn;
+			}
+		};
+	}
+
+	@LuanMethod public static Object[] gsub(LuanState luan,String s,String pattern,Object repl,Integer n) throws LuanException {
+		Utils.checkNotNull(s);
+		int max = n==null ? Integer.MAX_VALUE : n;
+		final Matcher m = Pattern.compile(pattern).matcher(s);
+		if( repl instanceof String ) {
+			String replacement = (String)repl;
+			int i = 0;
+			StringBuffer sb = new StringBuffer();
+			while( i<max && m.find() ) {
+				m.appendReplacement(sb,replacement);
+				i++;
+			}
+			m.appendTail(sb);
+			return new Object[]{ sb.toString(), i };
+		}
+		if( repl instanceof LuanTable ) {
+			LuanTable t = (LuanTable)repl;
+			int i = 0;
+			StringBuffer sb = new StringBuffer();
+			while( i<max && m.find() ) {
+				String match = m.groupCount()==0 ? m.group() : m.group(1);
+				Object val = t.get(luan,match);
+				if( val != null ) {
+					String replacement = luan.toString(val);
+					m.appendReplacement(sb,replacement);
+				}
+				i++;
+			}
+			m.appendTail(sb);
+			return new Object[]{ sb.toString(), i };
+		}
+		if( repl instanceof LuanFunction ) {
+			LuanFunction fn = (LuanFunction)repl;
+			int i = 0;
+			StringBuffer sb = new StringBuffer();
+			while( i<max && m.find() ) {
+				Object[] args;
+				final int count = m.groupCount();
+				if( count == 0 ) {
+					args = new String[]{m.group()};
+				} else {
+					args = new String[count];
+					for( int j=0; j<count; j++ ) {
+						args[j] = m.group(j+1);
+					}
+				}
+				Object val = Luan.first( fn.call(luan,args) );
+				if( val != null ) {
+					String replacement = luan.toString(val);
+					m.appendReplacement(sb,replacement);
+				}
+				i++;
+			}
+			m.appendTail(sb);
+			return new Object[]{ sb.toString(), i };
+		}
+		throw new LuanException( "bad argument #3 to 'gsub' (string/function/table expected)" );
+	}
+
+	// note - String.format() is too stupid to convert between ints and floats.
+	public static String format(String format,Object... args) {
+		return String.format(format,args);
+	}
+
+	public static String concat(LuanState luan,Object... args) throws LuanException {
+		StringBuilder sb = new StringBuilder();
+		for( Object arg : args ) {
+			sb.append( luan.toString(arg) );
+		}
+		return sb.toString();
+	}
+
+	public static String encode(String s) {
+		return Luan.stringEncode(s);
+	}
+
+	public static Number to_number(String s,Integer base) throws LuanException {
+		Utils.checkNotNull(s);
+		try {
+			if( base == null ) {
+				return Double.valueOf(s);
+			} else {
+				return Long.valueOf(s,base);
+			}
+		} catch(NumberFormatException e) {}
+		return null;
+	}
+
+	public static boolean matches(String s,String pattern) throws LuanException {
+		Utils.checkNotNull(s);
+		return Pattern.compile(pattern).matcher(s).find();
+	}
+
+	public static LuanTable split(String s,String pattern) throws LuanException {
+		Utils.checkNotNull(s);
+		return new LuanTable(Arrays.asList(s.split(pattern)));
+	}
+
+}