diff --git a/v4/ctx.py b/v4/ctx.py
index 5ca624d..af8f36e 100644
--- a/v4/ctx.py
+++ b/v4/ctx.py
@@ -32,10 +32,7 @@ class ctx_Controller:
     self.callbacks.append(cb)
 
   def registerFieldCallback(self, fieldName, cb):
-    def execCB(c):
-      if c.recentField == fieldName:
-        cb(c)
-    self.callbacks.append(execCB)
+    self.callbacks.append(lambda c: cb(c) if c.recentField == fieldName else None)
 
   def registerFunction(self, f):
     self.functions.append(f)
diff --git a/v4/ctx_test.cpp b/v4/ctx_test.cpp
new file mode 100644
index 0000000..fc38a80
--- /dev/null
+++ b/v4/ctx_test.cpp
@@ -0,0 +1,86 @@
+
+#include <map>
+#include <string>
+#include <vector>
+#include "ctx.h"
+#include "llm.h"
+#include "memory_Context.h"
+#include "main.h"
+
+std::string ctx_test_Controller_executeFunctions_set(
+) {
+  auto c = memory_createContext();
+  auto ctrl = ctx_Controller(c);
+  // Disable automatic invocation of executeFunctions.
+  ctrl.isProcessingQueue = true;
+  ctrl.set("input", "123");
+  ctrl.registerFunction(__processInput);
+  // Apply 'input'.
+  ctrl.executeFunctions();
+  // Apply 'outputHelp'.
+  ctrl.executeFunctions();
+  if (
+    c.input == "123" &&
+    c.outputHelp == "Checked"
+  ) {
+    return "OK: ctx_Controller_executeFunctions_set";
+  }
+  return "ERR: ctx_Controller_executeFunctions_set";
+}
+
+std::string ctx_test_Controller_processQueue(
+) {
+  auto c = memory_createContext();
+  auto ctrl = ctx_Controller(c);
+  ctrl.registerFunction(__processInput);
+  ctrl.set("input", "abc");;
+  if (
+    c.input == "abc" &&
+    c.outputHelp == "Checked"
+  ) {
+    return "OK: ctx_Controller_processQueue";
+  }
+  return "ERR: ctx_Controller_processQueue";
+}
+
+std::string ctx_test_memoryContext_field(
+) {
+  auto c = memory_createContext();
+  c.input = "abc";
+  if (
+    c.field("input") == "abc"
+  ) {
+    return "OK: ctx_memoryContext_field";
+  }
+  return "ERR: ctx_memoryContext_field";
+}
+
+std::string ctx_test_memoryContext_setField(
+) {
+  auto c = memory_createContext();
+  c.input = "abc";
+  c.setField("input", "123");
+  if (
+    c.field("input") == "123"
+  ) {
+    return "OK: ctx_memoryContext_setField";
+  }
+  return "ERR: ctx_memoryContext_setField";
+}
+
+// Auxiliary functions.
+
+memory_Context __processInput(
+  memory_Context c
+) {
+  if (
+    c.recentField == "input"
+  ) {
+    c.outputHelp = "Checked";
+    c.recentField = "outputHelp";
+    return c;
+  }
+  c.recentField = "none";
+  return c;
+}
+
diff --git a/v4/ctx_test.py b/v4/ctx_test.py
index 2179714..f20836d 100644
--- a/v4/ctx_test.py
+++ b/v4/ctx_test.py
@@ -66,7 +66,9 @@ def ctx_test_memoryContext_setField(
 # Auxiliary functions.
 
 @llm_by_value
-def __processInput(c):
+def __processInput(
+  c: memory_Context
+) -> memory_Context:
   if (
     c.recentField == "input"
   ):
diff --git a/v4/ctx_test2.py b/v4/ctx_test2.py
new file mode 100644
index 0000000..1a2bc83
--- /dev/null
+++ b/v4/ctx_test2.py
@@ -0,0 +1,142 @@
+from ctx import *
+from memory import *
+from memory_Context import *
+
+def ctx_test_Controller_executeFunctions_set(
+) -> str:
+  c = memory_createContext()
+  ctrl = ctx_Controller(c)
+  # Disable automatic invocation of executeFunctions.
+  ctrl.isProcessingQueue = True
+  ctrl.set("input", "123")
+
+  @llm_by_value
+  def processInput(c):
+    if (
+      c.recentField == "input"
+    ):
+      c.outputHelp = "Checked"
+      c.recentField = "outputHelp"
+      return c
+    #}
+    c.recentField = "none"
+    return c
+  #}
+
+  ctrl.registerFunction(processInput)
+  # Apply 'input'.
+  ctrl.executeFunctions()
+  # Apply 'outputHelp'.
+  ctrl.executeFunctions()
+  if (
+    c.input == "123" and
+    c.outputHelp == "Checked"
+  ):
+    return "OK: ctx_Controller_executeFunctions_set"
+  #}
+  return "ERR: ctx_Controller_executeFunctions_set"
+#}
+
+def ctx_test_Controller_processQueue(
+) -> str:
+  c = memory_createContext()
+  ctrl = ctx_Controller(c)
+
+  @llm_by_value
+  def processInput(c):
+    if (
+      c.recentField == "input"
+    ):
+      c.outputHelp = "Checked"
+      c.recentField = "outputHelp"
+      return c
+    #}
+    c.recentField = "none"
+    return c
+  #}
+
+  ctrl.registerFunction(processInput)
+  ctrl.set("input", "abc");
+  if (
+    c.input == "abc" and
+    c.outputHelp == "Checked"
+  ):
+    return "OK: ctx_Controller_processQueue"
+  #}
+  return "ERR: ctx_Controller_processQueue"
+#}
+
+def ctx_test_Controller_registerFieldCallback_match(
+) -> str:
+  c = memory_createContext()
+  ctrl = ctx_Controller(c)
+  c.input = "123"
+  c.recentField = "input"
+  
+  globals()["callbackInput"] = ""
+  def setCallbackInput(c):
+    if (
+      c.recentField == "input"
+    ):
+      globals()["callbackInput"] = c.input
+
+  ctrl.registerFieldCallback("input", setCallbackInput)
+  ctrl.reportContext()
+  if (
+    c.input == globals()["callbackInput"]
+  ):
+    return "OK: ctx_Controller_registerFieldCallback_match"
+  #}
+  return f"ERR: ctx_Controller_registerFieldCallback_match"
+#}
+
+def ctx_test_Controller_registerFieldCallback_mismatch(
+) -> str:
+  c = memory_createContext()
+  ctrl = ctx_Controller(c)
+  c.input = "123"
+  c.outputHelp = "you"
+  # A field other than 'input' is marked recent.
+  c.recentField = "outputHelp"
+
+  globals()["callbackInput"] = ""
+  def setCallbackInput(c):
+    if (
+      c.recentField == "input"
+    ):
+      globals()["callbackInput"] = c.input
+
+  ctrl.registerFieldCallback("input", setCallbackInput)
+  ctrl.reportContext()
+  if (
+    globals()["callbackInput"] == ""
+  ):
+    return "OK: ctx_Controller_registerFieldCallback_mismatch"
+  #}
+  return f"ERR: ctx_Controller_registerFieldCallback_mismatch"
+#}
+
+def ctx_test_memoryContext_field(
+) -> str:
+  c = memory_createContext()
+  c.input = "abc"
+  if (
+    c.field("input") == "abc"
+  ):
+    return "OK: ctx_memoryContext_field"
+  #}
+  return "ERR: ctx_memoryContext_field"
+#}
+
+def ctx_test_memoryContext_setField(
+) -> str:
+  c = memory_createContext()
+  c.input = "abc"
+  c.setField("input", "123")
+  if (
+    c.input == "123"
+  ):
+    return "OK: ctx_memoryContext_setField"
+  #}
+  return "ERR: ctx_memoryContext_setField"
+#}
diff --git a/v4/cxx-headers b/v4/cxx-headers
index eb8d0fc..7a69094 100755
--- a/v4/cxx-headers
+++ b/v4/cxx-headers
@@ -7,6 +7,7 @@ grep '^memory_Context ' memory.cpp > $TMP
 grep '^std::string ' memory_test.cpp >> $TMP
 grep '^memory_Context ' cli.cpp >> $TMP
 grep '^std::string ' cli_test.cpp >> $TMP
+grep '^std::string ' ctx_test.cpp >> $TMP
 grep '^std::string ' llm_test.cpp >> $TMP
 
 IN=$TMP
diff --git a/v4/gen-C++ b/v4/gen-C++
index 4f3d614..23c8529 100755
--- a/v4/gen-C++
+++ b/v4/gen-C++
@@ -6,4 +6,5 @@ c++ -o test_memory_C++ -std=c++11 -I. \
   llm_test.cpp \
   cli.cpp \
   cli_test.cpp \
+  ctx_test2.cpp \
   main.cpp
diff --git a/v4/main.h b/v4/main.h
index 3914930..3fd1d58 100644
--- a/v4/main.h
+++ b/v4/main.h
@@ -40,6 +40,10 @@ std::string cli_test_selectItem();
 std::string cli_test_showHelp_h();
 std::string cli_test_showHelp_help();
 std::string cli_test_reportVictory();
+std::string ctx_test_Controller_executeFunctions_set();
+std::string ctx_test_Controller_processQueue();
+std::string ctx_test_memoryContext_field();
+std::string ctx_test_memoryContext_setField();
 std::string llm_test_isDigit_digit();
 std::string llm_test_isDigit_notDigit();
 std::string llm_test_strToInt();
diff --git a/v4/main.py b/v4/main.py
index d6fbc4f..4409ca9 100644
--- a/v4/main.py
+++ b/v4/main.py
@@ -1,8 +1,9 @@
 from cli import *
 from cli_test import *
 from ctx import *
-from ctx_test import *
-from ctx_test_Python import *
+from ctx_test2 import *
+#from ctx_test import *
+#from ctx_test_Python import *
 from llm_test import *
 from llm_test_Python import *
 from memory_test import *
@@ -10,8 +11,8 @@ import sys
 
 print(ctx_test_Controller_executeFunctions_set())
 print(ctx_test_Controller_processQueue())
-print(ctx_test_Python_Controller_registerFieldCallback_match())
-print(ctx_test_Python_Controller_registerFieldCallback_mismatch())
+print(ctx_test_Controller_registerFieldCallback_match())
+print(ctx_test_Controller_registerFieldCallback_mismatch())
 print(ctx_test_memoryContext_field())
 print(ctx_test_memoryContext_setField())
 
diff --git a/v4/tPythonC++/CPP.py b/v4/tPythonC++/CPP.py
index 364f7cd..944c56e 100644
--- a/v4/tPythonC++/CPP.py
+++ b/v4/tPythonC++/CPP.py
@@ -55,6 +55,7 @@ def translateStatement(s, state):
     posColon = ss.find(": ")
     posComma = ss.find(", ")
     posComment = ss.find("# ")
+    posCtrl = ss.find("ctrl.")
     posCtx = ss.find("c.")
     posEqual = ss.find(" = ")
     posFor = ss.find("for ")
@@ -97,6 +98,7 @@ def translateStatement(s, state):
     # name = value -> auto name = value
     if (
         posCtx == -1 and
+        posCtrl == -1 and
         posColon == -1 and
         posOpenSquareBracket == -1 and
         posEqual >= 0
diff --git a/v4/translate-py-cxx b/v4/translate-py-cxx
index 2b29e66..fa010a3 100755
--- a/v4/translate-py-cxx
+++ b/v4/translate-py-cxx
@@ -7,5 +7,6 @@ $TR $DIR/memory.py > $DIR/memory.cpp
 $TR $DIR/memory_test.py > $DIR/memory_test.cpp
 $TR $DIR/cli.py > $DIR/cli.cpp
 $TR $DIR/cli_test.py > $DIR/cli_test.cpp
+$TR $DIR/ctx_test.py > $DIR/ctx_test.cpp
 $TR $DIR/llm_test.py > $DIR/llm_test.cpp
 $DIR/cxx-headers