Added basic lambda support.

src/main/java/com/samskivert/mustache/Mustache.java

@@ -150,7 +150,19 @@ public class Mustache
     {
         /** Returns a reader for the template with the supplied name.
          * @throws Exception if the template could not be loaded for any reason. */
-        public Reader getTemplate (String name) throws Exception;
+        Reader getTemplate (String name) throws Exception;
+    }
+
+    /** Used to handle lambdas. */
+    public interface Lambda
+    {
+        /** Executes this lambda on the supplied template fragment. The lambda should write its
+         * results to {@code out}.
+         *
+         * @param tmpl the fragment of the template that was passed to the lambda.
+         * @param out the writer to which the lambda should write its output.
+         */
+        void execute (Template.Fragment frag, Writer out) throws IOException;
     }
 
     /** Used to read variables from values. */
@@ -640,6 +652,12 @@ public class Mustache
                 if ((Boolean)value) {
                     executeSegs(tmpl, ctx, out);
                 }
+            } else if (value instanceof Lambda) {
+                try {
+                    ((Lambda)value).execute(tmpl.createFragment(_segs, ctx), out);
+                } catch (IOException ioe) {
+                    throw new MustacheException(ioe);
+                }
             } else if (_compiler.emptyStringIsFalse && "".equals(value)) {
                 // omit the section
             } else {

src/main/java/com/samskivert/mustache/Template.java

@@ -36,6 +36,22 @@ import java.util.Map;
  */
 public class Template
 {
+    /**
+     * Encapsulates a fragment of a template that is passed to a lambda. The fragment is bound to
+     * the variable context that was in effect at the time the lambda was called.
+     */
+    public abstract class Fragment {
+        /** Executes this template fragment, writing its result to {@code out}. */
+        public abstract void execute (Writer out);
+
+        /** Executes this template fragment and returns is result as a string. */
+        public String execute () {
+            StringWriter out = new StringWriter();
+            execute(out);
+            return out.toString();
+        }
+    }
+
     /**
      * Executes this template with the given context, returning the results as a string.
      * @throws MustacheException if an error occurs while executing or writing the template.
@@ -73,7 +89,7 @@ public class Template
     {
         _segs = segs;
         _compiler = compiler;
-        _fcache = _compiler.collector.createFetcherCache();
+        _fcache = compiler.collector.createFetcherCache();
     }
 
     protected void executeSegs (Context ctx, Writer out) throws MustacheException
@@ -83,6 +99,17 @@ public class Template
         }
     }
 
+    protected Fragment createFragment (final Segment[] segs, final Context ctx)
+    {
+        return new Fragment() {
+            @Override public void execute (Writer out) {
+                for (Segment seg : segs) {
+                    seg.execute(Template.this, ctx, out);
+                }
+            }
+        };
+    }
+
     /**
      * Called by executing segments to obtain the value of the specified variable in the supplied
      * context.