output

system ~/projects/jruby $ jirb
>> require 'java'
=> true
>> binding = Thread.current.to_java.getContext.nth_binding(4)
=> #<Java::OrgJrubyRuntime::Binding:0x304648>
>> binding = org.jruby.RubyBinding.new(JRuby.runtime, JRuby.runtime.binding, binding)
=> #<Binding:0x8b3bb3>
>> binding = JRuby.dereference(binding)
=> #<Binding:0x8b3bb3>
>> eval "__FILE__", binding
=> "/Users/headius/projects/jruby/lib/ruby/1.8/irb.rb"

patch

diff --git a/src/org/jruby/runtime/ThreadContext.java b/src/org/jruby/runtime/ThreadContext.java
index 383efd9..6c1cdcb 100644
--- a/src/org/jruby/runtime/ThreadContext.java
+++ b/src/org/jruby/runtime/ThreadContext.java
@@ -229,6 +229,10 @@ public final class ThreadContext {
     public DynamicScope getPreviousScope() {
         return scopeStack[scopeIndex - 1];
     }
+
+    public DynamicScope getNthPreviousScope(int n) {
+        return scopeStack[scopeIndex - n];
+    }
     
     private void expandFramesIfNecessary() {
         int newSize = frameStack.length * 2;
@@ -434,6 +438,11 @@ public final class ThreadContext {
         int index = frameIndex;
         return index < 1 ? null : frameStack[index - 1];
     }
+
+    public Frame getNthPreviousFrame(int n) {
+        int index = frameIndex;
+        return index < n ? null : frameStack[index - n];
+    }
     
     public int getFrameCount() {
         return frameIndex + 1;
@@ -635,6 +644,12 @@ public final class ThreadContext {
         RubyModule parentModule = parentStack[parentIndex - 1];
         return parentModule.getNonIncludedClass();
     }
+
+    public RubyModule getNthPreviousRubyClass(int n) {
+        assert parentIndex - n >= 0  : "Trying to get RubyClass from too-shallow stack";
+        RubyModule parentModule = parentStack[parentIndex - n];
+        return parentModule.getNonIncludedClass();
+    }
     
     public boolean getConstantDefined(String internedName) {
         IRubyObject value = getConstant(internedName);
@@ -1241,6 +1256,22 @@ public final class ThreadContext {
     }
 
     /**
+     * Return a binding representing the nth previous call's state.
+     *
+     * Only interesting for experimentation; interpreted mode is recommended.
+     *
+     * @return the nth caller's binding.
+     */
+    public Binding nthBinding(int n) {
+        if (n == 1) {
+            return previousBinding();
+        } else {
+            Frame frame = getNthPreviousFrame(n);
+            return new Binding(frame, getNthPreviousRubyClass(n), getNthPreviousScope(n - 1), backtrace[backtraceIndex - (n - 1)].clone());
+        }
+    }
+
+    /**
      * Return a binding representing the previous call's state
      * @return the current binding
      */