ExpressionParser: Move FunctionExpression type definitions into another file.

Source/Core/InputCommon/ControlReference/FunctionExpression.h

@@ -0,0 +1,41 @@
+// Copyright 2019 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "InputCommon/ControlReference/ExpressionParser.h"
+#include "InputCommon/ControlReference/FunctionExpression.h"
+
+namespace ciface
+{
+namespace ExpressionParser
+{
+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);
+
+protected:
+  virtual std::string GetFuncName() const = 0;
+  virtual bool ValidateArguments(const std::vector<std::unique_ptr<Expression>>& args) = 0;
+
+  Expression& GetArg(u32 number);
+  const Expression& GetArg(u32 number) const;
+
+private:
+  std::vector<std::unique_ptr<Expression>> m_args;
+};
+
+std::unique_ptr<FunctionExpression> MakeFunctionExpression(std::string name);
+
+}  // namespace ExpressionParser
+}  // namespace ciface