Prompt functions

see page 767-768 for many prompt functions

• #include "prompt.h"
  string PromptString(const string & prompt) // post: returns string entered by user { string word; cout << prompt; cin >> word; return word; } bool PromptYesNo(string prompt) // postcondition: returns true iff user enters yes { string str; char ch; do { cout << prompt << " "; cin >> str; ch = tolower(str[0]); } while (ch != 'y' && ch != 'n'); return ch == 'y'; }

Input File Streams

Declaring a file stream to read from instead of cin

1. #include <fstream>;

2. declare an ifstream variable

      ifstream readin;
   

3. open filestream bounding it to a file

      string file = "words";
      readin.open(file.c_str());
   

4. use your variable instead of cin to read

      string word;
      readin >> word;
   

5. close file stream when done

      readin.close();
   

Can create an output stream to write to instead of cout

• use ofstream

First part of Today's Classwork

• countw2.cpp

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Iterator class

programing pattern (Iteration) you will see over and over

process all the "entries" in the class

Example: StringSetIterator - process all the words in a set

Algorithm

• create iterator
• position at first word
• while (current entry is valid)
  • process current entry
  • move to next entry

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Set Class for strings

set - collection of items with no duplicates

class StringSet { public: StringSet(); StringSet(int isize); // initialize size -- for efficiency // accessors bool contains(const string& s) const; // true if s in the set int size() const; // returns number of items in set // mutators void insert(const string& s); // inserts s in set void erase (const string& s); // removes s from set void clear(); // removes all items from set private: // not shown }; class StringSetIterator { public: StringSetIterator(const StringSet& s); void Init() const; bool HasMore() const; void Next() const; string Current() const; private: // not shown };

Example

Note: even though the StringSet changes, the iterator uses the changed StringSet

#include <iostream> #include <string> using namespace std; #include "utils.h" #include "stringset.h" int main() { StringSet A; A.insert("sad"); A.insert("fun"); A.insert("sad"); A.insert("tickle"); A.insert("sad"); StringSetIterator T(A); for (T.Init(); T.HasMore(); T.Next()) { cout << T.Current() << endl; } cout << endl; A.erase("sad"); for (T.Init(); T.HasMore(); T.Next()) { cout << T.Current() << endl; } cout << endl; A.clear(); for (T.Init(); T.HasMore(); T.Next()) { cout << T.Current() << endl; } cout << endl; WaitForReturn(); return 0; }



What is output?

Second Part of Today's Classwork

• countw3.cpp