Lecture Notes for Advanced Programming II

7 December 2001 - Assignment 5 Code Review

Line Statistics - Newlines

Statistics derived from all files ending in .cc, .cpp, .CC, .C, and .h.

Line Statistics - Semicolons

Statistics derived from all files ending in .cc, .cpp, .CC, .C, and .h.

Procedure Statistics

Statistics derived from all files ending in .cc, .cpp, .CC, .C, and .h.

File Statistics

Statistics derived from all files ending in .cc, .cpp, .CC, .C, and .h.

Design

• Most people defined a graph and manipulated that.

• Separate concerns.

  • Graphs don't need to know about commands.

    void remove_edge(
      map<string, Command> & graph,
      stack<Command> & undo_stack,
      stack<Command> & redo_stack,
      Command v);
    

  • Separated concerns are easier to understand and change.

  • They are a bit harder to design, but not for long.

• Use the proper data structure.

  • Storing commands in two stacks.

    • A undo and a redo stack.

    • Moving commands from one stack to the other.

  • Storing commands in a list.

    • A pointer indicates the next command to undo or redo.

    • Much simpler, less effort, fewer pieces.

An Alternative Design

• Don't bother with a graph, just store the commands.

• Keep track of the most recently executed command.

• When it comes time to print, execute the commands, print the result.

• This is known as lazy evaluation.

  • The other commands become easier, print becomes harder.

  • If print is an infrequent operation, this design wins.

  • Error detection is a bit harder.

Write Smart Code

• Demonstrate mastery over concepts.

  while (getline(cin, graphline)) {
    if (cin.eof()) break;
    // whatever
    }
  

• Write meaningful comments.

  • These comments aren't helpful.

    // main function
    int main() {
    
    // main
    int main() {
    
    // main function
    int main(int args, char* argv[]) {
    

  • Document action, not things.

    static bool read_cmd(std::istream & is, cmd & c) {
    
      // Read the next command from is and store it in c.
    

Demonstrate Learning Behavior

• What's wrong with this class?

  class Node {
  
    friend class ListInt;
  
    private:
  
      char* label;
      Node* next;
      int label_length;
  
    public:
  
      Node();
      Node(const Node& p);
      Node(char* p,  Node* ptr);
      void set_label(char*,Node*);
      char* get_label() const;
      Node* get_next() const;
      void display_node() const;
    };
  

• This code is still generating garbage.

  Node::Node(const Node& p) {
    assert(p.get_label() != NULL);
    label = new char[strlen(p.get_label()) + 1];
    label = '\0';
    strcpy(label, p.get_label());
    next = p.get_next();
    }
  

General Tips

• Try to avoid #defines.

  • They don't obey scoping rules.

    #define NODE "node"
    #define EDGE "edge"
    #define UNDO "undo"
    #define REDO "redo"
    

  • Use consts instead.

    const char * NODE = "node";
    const char * EDGE = "edge";
    const char * UNDO = "undo";
    const char * REDO = "redo";
    

This page last modified on 14 December 2001.