class ProgramNodeBuilder {
public:
  ProgramNodeBuilder();
  virtual ProgramNode* NewVariable(
    const char* variableName
  ) const;
  virtual ProgramNode* NewAssignment(
    ProgramNode* variable, ProgramNode* expression
  ) const;
  virtual ProgramNode* NewReturnStatement(
    ProgramNode* value
  ) const;
  virtual ProgramNode* NewCondition(
    ProgramNode* condition,
    ProgramNode* truePart, ProgramNode* falsePart
  ) const;
  // ...
  ProgramNode* GetRootNode();
private:
  ProgramNode* _node;
};