diff --git a/Source/Core/DolphinQt/Config/Mapping/IOWindow.cpp b/Source/Core/DolphinQt/Config/Mapping/IOWindow.cpp
index aacaa3ae89..16058c2aa2 100644
--- a/Source/Core/DolphinQt/Config/Mapping/IOWindow.cpp
+++ b/Source/Core/DolphinQt/Config/Mapping/IOWindow.cpp
@@ -81,7 +81,7 @@ QTextCharFormat GetVariableCharFormat()
   return format;
 }
 
-QTextCharFormat GetFunctionCharFormat()
+QTextCharFormat GetBarewordCharFormat()
 {
   QTextCharFormat format;
   format.setForeground(QBrush{Qt::darkCyan});
@@ -125,8 +125,8 @@ void ControlExpressionSyntaxHighlighter::highlightBlock(const QString& text)
     case TokenType::TOK_CONTROL:
       char_format = GetControlCharFormat();
       break;
-    case TokenType::TOK_FUNCTION:
-      char_format = GetFunctionCharFormat();
+    case TokenType::TOK_BAREWORD:
+      char_format = GetBarewordCharFormat();
       break;
     case TokenType::TOK_VARIABLE:
       char_format = GetVariableCharFormat();
@@ -220,16 +220,15 @@ void IOWindow::CreateMainLayout()
   m_functions_combo = new QComboBox();
   m_functions_combo->addItem(tr("Functions"));
   m_functions_combo->insertSeparator(1);
-  m_functions_combo->addItem(QStringLiteral("!if"));
-  m_functions_combo->addItem(QStringLiteral("!sin"));
-  m_functions_combo->addItem(QStringLiteral("!timer"));
-  m_functions_combo->addItem(QStringLiteral("!toggle"));
-  m_functions_combo->addItem(QStringLiteral("!deadzone"));
-  m_functions_combo->addItem(QStringLiteral("!smooth"));
-  m_functions_combo->addItem(QStringLiteral("!hold"));
-  m_functions_combo->addItem(QStringLiteral("!tap"));
-  m_functions_combo->addItem(QStringLiteral("!relative"));
-  m_functions_combo->addItem(QStringLiteral("!pulse"));
+  m_functions_combo->addItem(QStringLiteral("if"));
+  m_functions_combo->addItem(QStringLiteral("timer"));
+  m_functions_combo->addItem(QStringLiteral("toggle"));
+  m_functions_combo->addItem(QStringLiteral("deadzone"));
+  m_functions_combo->addItem(QStringLiteral("smooth"));
+  m_functions_combo->addItem(QStringLiteral("hold"));
+  m_functions_combo->addItem(QStringLiteral("tap"));
+  m_functions_combo->addItem(QStringLiteral("relative"));
+  m_functions_combo->addItem(QStringLiteral("pulse"));
 
   // Devices
   m_main_layout->addWidget(m_devices_combo);
diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
index a686e8fcc4..f7937a19bd 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
@@ -21,42 +21,6 @@ namespace ciface::ExpressionParser
 {
 using namespace ciface::Core;
 
-inline std::string OpName(TokenType op)
-{
-  switch (op)
-  {
-  case TOK_AND:
-    return "And";
-  case TOK_OR:
-    return "Or";
-  case TOK_FUNCTION:
-    return "Function";
-  case TOK_ADD:
-    return "Add";
-  case TOK_SUB:
-    return "Sub";
-  case TOK_MUL:
-    return "Mul";
-  case TOK_DIV:
-    return "Div";
-  case TOK_MOD:
-    return "Mod";
-  case TOK_ASSIGN:
-    return "Assign";
-  case TOK_LTHAN:
-    return "LThan";
-  case TOK_GTHAN:
-    return "GThan";
-  case TOK_COMMA:
-    return "Comma";
-  case TOK_VARIABLE:
-    return "Var";
-  default:
-    assert(false);
-    return "";
-  }
-}
-
 Token::Token(TokenType type_) : type(type_)
 {
 }
@@ -70,55 +34,6 @@ bool Token::IsBinaryOperator() const
   return type >= TOK_BINARY_OPS_BEGIN && type < TOK_BINARY_OPS_END;
 }
 
-Token::operator std::string() const
-{
-  switch (type)
-  {
-  case TOK_DISCARD:
-    return "Discard";
-  case TOK_EOF:
-    return "EOF";
-  case TOK_LPAREN:
-    return "(";
-  case TOK_RPAREN:
-    return ")";
-  case TOK_AND:
-    return "&";
-  case TOK_OR:
-    return "|";
-  case TOK_FUNCTION:
-    return '!' + data;
-  case TOK_ADD:
-    return "+";
-  case TOK_SUB:
-    return "-";
-  case TOK_MUL:
-    return "*";
-  case TOK_DIV:
-    return "/";
-  case TOK_MOD:
-    return "%";
-  case TOK_ASSIGN:
-    return "=";
-  case TOK_LTHAN:
-    return "<";
-  case TOK_GTHAN:
-    return ">";
-  case TOK_COMMA:
-    return ",";
-  case TOK_CONTROL:
-    return "Device(" + data + ')';
-  case TOK_LITERAL:
-    return '\'' + data + '\'';
-  case TOK_VARIABLE:
-    return '$' + data;
-  default:
-    break;
-  }
-
-  return "Invalid";
-}
-
 Lexer::Lexer(const std::string& expr_) : expr(expr_)
 {
   it = expr.begin();
@@ -134,21 +49,12 @@ std::string Lexer::FetchDelimString(char delim)
 
 std::string Lexer::FetchWordChars()
 {
-  // Words must start with a letter or underscore.
-  if (expr.end() == it || (!std::isalpha(*it, std::locale::classic()) && ('_' != *it)))
-    return "";
-
   // Valid word characters:
   std::regex rx(R"([a-z\d_])", std::regex_constants::icase);
 
   return FetchCharsWhile([&rx](char c) { return std::regex_match(std::string(1, c), rx); });
 }
 
-Token Lexer::GetFunction()
-{
-  return Token(TOK_FUNCTION, FetchWordChars());
-}
-
 Token Lexer::GetDelimitedLiteral()
 {
   return Token(TOK_LITERAL, FetchDelimString('\''));
@@ -164,21 +70,15 @@ Token Lexer::GetFullyQualifiedControl()
   return Token(TOK_CONTROL, FetchDelimString('`'));
 }
 
-Token Lexer::GetBarewordsControl(char c)
+Token Lexer::GetBareword(char first_char)
 {
-  std::string name;
-  name += c;
-  name += FetchCharsWhile([](char c) { return std::isalpha(c, std::locale::classic()); });
-
-  ControlQualifier qualifier;
-  qualifier.control_name = name;
-  return Token(TOK_CONTROL, qualifier);
+  return Token(TOK_BAREWORD, first_char + FetchWordChars());
 }
 
-Token Lexer::GetRealLiteral(char c)
+Token Lexer::GetRealLiteral(char first_char)
 {
   std::string value;
-  value += c;
+  value += first_char;
   value += FetchCharsWhile([](char c) { return isdigit(c, std::locale::classic()) || ('.' == c); });
 
   if (std::regex_match(value, std::regex(R"(\d+(\.\d+)?)")))
@@ -209,7 +109,7 @@ Token Lexer::NextToken()
   case '|':
     return Token(TOK_OR);
   case '!':
-    return GetFunction();
+    return Token(TOK_NOT);
   case '+':
     return Token(TOK_ADD);
   case '-':
@@ -236,7 +136,7 @@ Token Lexer::NextToken()
     return GetFullyQualifiedControl();
   default:
     if (isalpha(c, std::locale::classic()))
-      return GetBarewordsControl(c);
+      return GetBareword(c);
     else if (isdigit(c, std::locale::classic()))
       return GetRealLiteral(c);
     else
@@ -300,7 +200,6 @@ public:
     input = env.FindInput(qualifier);
     output = env.FindOutput(qualifier);
   }
-  operator std::string() const override { return "`" + static_cast<std::string>(qualifier) + "`"; }
 
 private:
   ControlQualifier qualifier;
@@ -384,11 +283,6 @@ public:
     lhs->UpdateReferences(env);
     rhs->UpdateReferences(env);
   }
-
-  operator std::string() const override
-  {
-    return OpName(op) + "(" + std::string(*lhs) + ", " + std::string(*rhs) + ")";
-  }
 };
 
 class LiteralExpression : public Expression
@@ -406,8 +300,6 @@ public:
     // Nothing needed.
   }
 
-  operator std::string() const override { return '\'' + GetName() + '\''; }
-
 protected:
   virtual std::string GetName() const = 0;
 };
@@ -450,8 +342,6 @@ public:
     m_value_ptr = env.GetVariablePtr(m_name);
   }
 
-  operator std::string() const override { return '$' + m_name; }
-
 protected:
   const std::string m_name;
   ControlState* m_value_ptr{};
@@ -471,12 +361,6 @@ public:
   void SetValue(ControlState value) override { GetActiveChild()->SetValue(value); }
 
   int CountNumControls() const override { return GetActiveChild()->CountNumControls(); }
-  operator std::string() const override
-  {
-    return "Coalesce(" + static_cast<std::string>(*m_lhs) + ", " +
-           static_cast<std::string>(*m_rhs) + ')';
-  }
-
   void UpdateReferences(ControlEnvironment& env) override
   {
     m_lhs->UpdateReferences(env);
@@ -566,19 +450,6 @@ public:
   }
 
 private:
-  struct FunctionArguments
-  {
-    FunctionArguments(ParseResult&& result_, std::vector<std::unique_ptr<Expression>>&& args_ = {})
-        : result(std::move(result_)), args(std::move(args_))
-    {
-    }
-
-    // Note: expression member isn't being used.
-    ParseResult result;
-
-    std::vector<std::unique_ptr<Expression>> args;
-  };
-
   const std::vector<Token>& tokens;
   std::vector<Token>::const_iterator m_it;
 
@@ -598,75 +469,81 @@ private:
     return tok.type == type;
   }
 
-  FunctionArguments ParseFunctionArguments()
+  ParseResult ParseFunctionArguments(std::unique_ptr<FunctionExpression>&& func,
+                                     const Token& func_tok)
   {
     std::vector<std::unique_ptr<Expression>> args;
 
     if (TOK_LPAREN != Peek().type)
     {
       // Single argument with no parens (useful for unary ! function)
-      auto arg = ParseAtom(Chew());
+      const auto tok = Chew();
+      auto arg = ParseAtom(tok);
       if (ParseStatus::Successful != arg.status)
-        return {std::move(arg)};
+        return arg;
 
       args.emplace_back(std::move(arg.expr));
-      return {ParseResult::MakeSuccessfulResult({}), std::move(args)};
     }
-
-    // Chew the L-Paren
-    Chew();
-
-    // Check for empty argument list:
-    if (TOK_RPAREN == Peek().type)
+    else
     {
+      // Chew the L-Paren
       Chew();
-      return {ParseResult::MakeSuccessfulResult({})};
+
+      // Check for empty argument list:
+      if (TOK_RPAREN == Peek().type)
+      {
+        Chew();
+      }
+      else
+      {
+        while (true)
+        {
+          // Read one argument.
+          // Grab an expression, but stop at comma.
+          auto arg = ParseBinary(BinaryOperatorPrecedence(TOK_COMMA));
+          if (ParseStatus::Successful != arg.status)
+            return arg;
+
+          args.emplace_back(std::move(arg.expr));
+
+          // Right paren is the end of our arguments.
+          const Token tok = Chew();
+          if (TOK_RPAREN == tok.type)
+            break;
+
+          // Comma before the next argument.
+          if (TOK_COMMA != tok.type)
+            return ParseResult::MakeErrorResult(tok, _trans("Expected comma."));
+        };
+      }
     }
 
-    while (true)
+    if (!func->SetArguments(std::move(args)))
     {
-      // Read one argument.
-      // Grab an expression, but stop at comma.
-      auto arg = ParseBinary(BinaryOperatorPrecedence(TOK_COMMA));
-      if (ParseStatus::Successful != arg.status)
-        return {std::move(arg)};
-
-      args.emplace_back(std::move(arg.expr));
-
-      // Right paren is the end of our arguments.
-      const Token tok = Chew();
-      if (TOK_RPAREN == tok.type)
-        return {ParseResult::MakeSuccessfulResult({}), std::move(args)};
-
-      // Comma before the next argument.
-      if (TOK_COMMA != tok.type)
-        return {ParseResult::MakeErrorResult(tok, _trans("Expected comma."))};
+      // TODO: It would be nice to output how many arguments are expected.
+      return ParseResult::MakeErrorResult(func_tok, _trans("Wrong number of arguments."));
     }
+
+    return ParseResult::MakeSuccessfulResult(std::move(func));
   }
 
   ParseResult ParseAtom(const Token& tok)
   {
     switch (tok.type)
     {
-    case TOK_FUNCTION:
+    case TOK_BAREWORD:
     {
       auto func = MakeFunctionExpression(tok.data);
 
       if (!func)
-        return ParseResult::MakeErrorResult(tok, _trans("Unknown function."));
-
-      auto args = ParseFunctionArguments();
-
-      if (ParseStatus::Successful != args.result.status)
-        return std::move(args.result);
-
-      if (!func->SetArguments(std::move(args.args)))
       {
-        // TODO: It would be nice to output how many arguments are expected.
-        return ParseResult::MakeErrorResult(tok, _trans("Wrong number of arguments."));
+        // Invalid function, interpret this as a bareword control.
+        Token control_tok(tok);
+        control_tok.type = TOK_CONTROL;
+        return ParseAtom(control_tok);
       }
 
-      return ParseResult::MakeSuccessfulResult(std::move(func));
+      return ParseFunctionArguments(std::move(func), tok);
     }
     case TOK_CONTROL:
     {
@@ -674,6 +551,10 @@ private:
       cq.FromString(tok.data);
       return ParseResult::MakeSuccessfulResult(std::make_unique<ControlExpression>(cq));
     }
+    case TOK_NOT:
+    {
+      return ParseFunctionArguments(MakeFunctionExpression("not"), tok);
+    }
     case TOK_LITERAL:
     {
       return MakeLiteralExpression(tok);
@@ -690,16 +571,13 @@ private:
     {
       // An atom was expected but we got a subtraction symbol.
       // Interpret it as a unary minus function.
-
-      // Make sure to copy the existing string position values for proper error results.
-      Token func = tok;
-      func.type = TOK_FUNCTION;
-      func.data = "minus";
-      return ParseAtom(std::move(func));
+      return ParseFunctionArguments(MakeFunctionExpression("minus"), tok);
     }
     default:
+    {
       return ParseResult::MakeErrorResult(tok, _trans("Expected start of expression."));
     }
+    }
   }
 
   static int BinaryOperatorPrecedence(TokenType type)
diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.h b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
index 3dac67e9db..2f41d2fde7 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.h
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
@@ -20,10 +20,11 @@ enum TokenType
   TOK_EOF,
   TOK_LPAREN,
   TOK_RPAREN,
-  TOK_FUNCTION,
+  TOK_NOT,
   TOK_CONTROL,
   TOK_LITERAL,
   TOK_VARIABLE,
+  TOK_BAREWORD,
   // Binary Ops:
   TOK_BINARY_OPS_BEGIN,
   TOK_AND = TOK_BINARY_OPS_BEGIN,
@@ -54,7 +55,6 @@ public:
   Token(TokenType type_, std::string data_);
 
   bool IsBinaryOperator() const;
-  operator std::string() const;
 };
 
 enum class ParseStatus
@@ -89,11 +89,10 @@ private:
 
   std::string FetchDelimString(char delim);
   std::string FetchWordChars();
-  Token GetFunction();
   Token GetDelimitedLiteral();
   Token GetVariable();
   Token GetFullyQualifiedControl();
-  Token GetBarewordsControl(char c);
+  Token GetBareword(char c);
   Token GetRealLiteral(char c);
 
   Token NextToken();
@@ -164,7 +163,6 @@ public:
   virtual void SetValue(ControlState state) = 0;
   virtual int CountNumControls() const = 0;
   virtual void UpdateReferences(ControlEnvironment& finder) = 0;
-  virtual operator std::string() const = 0;
 };
 
 class ParseResult
diff --git a/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp b/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp
index 6c3f10ad74..daf36c0fa1 100644
--- a/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp
+++ b/Source/Core/InputCommon/ControlReference/FunctionExpression.cpp
@@ -17,7 +17,7 @@ constexpr ControlState CONDITION_THRESHOLD = 0.5;
 using Clock = std::chrono::steady_clock;
 using FSec = std::chrono::duration<ControlState>;
 
-// usage: !toggle(toggle_state_input, [clear_state_input])
+// usage: toggle(toggle_state_input, [clear_state_input])
 class ToggleExpression : public FunctionExpression
 {
 private:
@@ -49,14 +49,11 @@ private:
     return m_state;
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "toggle"; }
-
   mutable bool m_released{};
   mutable bool m_state{};
 };
 
-// usage: !not(expression)
+// usage: not(expression)
 class NotExpression : public FunctionExpression
 {
 private:
@@ -67,10 +64,9 @@ private:
 
   ControlState GetValue() const override { return 1.0 - GetArg(0).GetValue(); }
   void SetValue(ControlState value) override { GetArg(0).SetValue(1.0 - value); }
-  std::string GetFuncName() const override { return ""; }
 };
 
-// usage: !sin(expression)
+// usage: sin(expression)
 class SinExpression : public FunctionExpression
 {
 private:
@@ -80,11 +76,9 @@ private:
   }
 
   ControlState GetValue() const override { return std::sin(GetArg(0).GetValue()); }
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "sin"; }
 };
 
-// usage: !timer(seconds)
+// usage: timer(seconds)
 class TimerExpression : public FunctionExpression
 {
 private:
@@ -118,14 +112,12 @@ private:
 
     return progress;
   }
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "timer"; }
 
 private:
   mutable Clock::time_point m_start_time = Clock::now();
 };
 
-// usage: !if(condition, true_expression, false_expression)
+// usage: if(condition, true_expression, false_expression)
 class IfExpression : public FunctionExpression
 {
 private:
@@ -139,12 +131,9 @@ private:
     return (GetArg(0).GetValue() > CONDITION_THRESHOLD) ? GetArg(1).GetValue() :
                                                           GetArg(2).GetValue();
   }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "if"; }
 };
 
-// usage: !minus(expression)
+// usage: minus(expression)
 class UnaryMinusExpression : public FunctionExpression
 {
 private:
@@ -158,12 +147,9 @@ private:
     // Subtraction for clarity:
     return 0.0 - GetArg(0).GetValue();
   }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "minus"; }
 };
 
-// usage: !deadzone(input, amount)
+// usage: deadzone(input, amount)
 class DeadzoneExpression : public FunctionExpression
 {
   virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
@@ -177,12 +163,9 @@ class DeadzoneExpression : public FunctionExpression
     const ControlState deadzone = GetArg(1).GetValue();
     return std::copysign(std::max(0.0, std::abs(val) - deadzone) / (1.0 - deadzone), val);
   }
-
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "deadzone"; }
 };
 
-// usage: !smooth(input, seconds_up, seconds_down = seconds_up)
+// usage: smooth(input, seconds_up, seconds_down = seconds_up)
 // seconds is seconds to change from 0.0 to 1.0
 class SmoothExpression : public FunctionExpression
 {
@@ -218,15 +201,12 @@ class SmoothExpression : public FunctionExpression
     return m_value;
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "smooth"; }
-
 private:
   mutable ControlState m_value = 0.0;
   mutable Clock::time_point m_last_update = Clock::now();
 };
 
-// usage: !hold(input, seconds)
+// usage: hold(input, seconds)
 class HoldExpression : public FunctionExpression
 {
   virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
@@ -256,15 +236,12 @@ class HoldExpression : public FunctionExpression
     return m_state;
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "smooth"; }
-
 private:
   mutable bool m_state = false;
   mutable Clock::time_point m_start_time = Clock::now();
 };
 
-// usage: !tap(input, seconds, taps=2)
+// usage: tap(input, seconds, taps=2)
 class TapExpression : public FunctionExpression
 {
   virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
@@ -313,16 +290,13 @@ class TapExpression : public FunctionExpression
     return 0.0;
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "tap"; }
-
 private:
   mutable bool m_released = true;
   mutable u32 m_taps = 0;
   mutable Clock::time_point m_start_time = Clock::now();
 };
 
-// usage: !relative(input, speed, [max_abs_value, [shared_state]])
+// usage: relative(input, speed, [max_abs_value, [shared_state]])
 // speed is max movement per second
 class RelativeExpression : public FunctionExpression
 {
@@ -337,15 +311,15 @@ class RelativeExpression : public FunctionExpression
     //
     // e.g. A single mapping with a relatively adjusted value between 0.0 and 1.0
     // Potentially useful for a trigger input
-    //  !relative(`Up` - `Down`, 2.0)
+    //  relative(`Up` - `Down`, 2.0)
     //
     // e.g. A value with two mappings (such as analog stick Up/Down)
     // The shared state allows the two mappings to work together.
     // This mapping (for up) returns a value clamped between 0.0 and 1.0
-    //  !relative(`Up`, 2.0, 1.0, $y)
+    //  relative(`Up`, 2.0, 1.0, $y)
     // This mapping (for down) returns the negative value clamped between 0.0 and 1.0
     // (Adjustments created by `Down` are applied negatively to the shared state)
-    //  !relative(`Down`, 2.0, -1.0, $y)
+    //  relative(`Down`, 2.0, -1.0, $y)
 
     const auto now = Clock::now();
 
@@ -373,15 +347,12 @@ class RelativeExpression : public FunctionExpression
     return std::max(0.0, m_state * std::copysign(1.0, max_abs_value));
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "relative"; }
-
 private:
   mutable ControlState m_state = 0.0;
   mutable Clock::time_point m_last_update = Clock::now();
 };
 
-// usage: !pulse(input, seconds)
+// usage: pulse(input, seconds)
 class PulseExpression : public FunctionExpression
 {
   virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) override
@@ -424,9 +395,6 @@ class PulseExpression : public FunctionExpression
     return m_state;
   }
 
-  void SetValue(ControlState value) override {}
-  std::string GetFuncName() const override { return "pulse"; }
-
 private:
   mutable bool m_released = false;
   mutable bool m_state = false;
@@ -435,7 +403,7 @@ private:
 
 std::unique_ptr<FunctionExpression> MakeFunctionExpression(std::string name)
 {
-  if (name.empty())
+  if ("not" == name)
     return std::make_unique<NotExpression>();
   else if ("if" == name)
     return std::make_unique<IfExpression>();
@@ -479,16 +447,6 @@ void FunctionExpression::UpdateReferences(ControlEnvironment& env)
     arg->UpdateReferences(env);
 }
 
-FunctionExpression::operator std::string() const
-{
-  std::string result = '!' + GetFuncName();
-
-  for (auto& arg : m_args)
-    result += ' ' + static_cast<std::string>(*arg);
-
-  return result;
-}
-
 bool FunctionExpression::SetArguments(std::vector<std::unique_ptr<Expression>>&& args)
 {
   m_args = std::move(args);
@@ -511,5 +469,9 @@ u32 FunctionExpression::GetArgCount() const
   return u32(m_args.size());
 }
 
+void FunctionExpression::SetValue(ControlState)
+{
+}
+
 }  // namespace ExpressionParser
 }  // namespace ciface
diff --git a/Source/Core/InputCommon/ControlReference/FunctionExpression.h b/Source/Core/InputCommon/ControlReference/FunctionExpression.h
index 35e000a16f..14b438a299 100644
--- a/Source/Core/InputCommon/ControlReference/FunctionExpression.h
+++ b/Source/Core/InputCommon/ControlReference/FunctionExpression.h
@@ -20,12 +20,12 @@ class FunctionExpression : public Expression
 public:
   int CountNumControls() const override;
   void UpdateReferences(ControlEnvironment& env) override;
-  operator std::string() const override;
 
   bool SetArguments(std::vector<std::unique_ptr<Expression>>&& args);
 
+  void SetValue(ControlState value) override;
+
 protected:
-  virtual std::string GetFuncName() const = 0;
   virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) = 0;
 
   Expression& GetArg(u32 number);