implement forward and back features using browserhistory.h and main.cpp and create a new source file (browserhistory.cpp) that runs with no failed tests.

(browserhistory.h)

#ifndef BROWSERHISTORY_H #define BROWSERHISTORY_H #include  #include  using namespace std; class BrowserHistory { public: // Creates a new browser history with only one page visited: default_url BrowserHistory(string default_url); // Returns the current page. string current_url(); // Moves the browser to a new page url via, // e.g., clicking a link, typing into the address bar, etc. void go_to_url(string url); // Moves back (into the past) by one url. // // If there is no past url to move to, does nothing. void back(); // Returns whether there is a url in the past, // i.e. whether the back button can be pushed. bool can_go_back(); // Returns how many urls are in the past, // i.e. how many times in a row the back button could be pushed. int past_url_count(); // Moves forward (into the future) by one url. // // If there is no future url to move to, does nothing. void forward(); // Returns whether there is a url in future, // i.e. whether the future button can be pushed. bool can_go_forward(); // Returns how many urls are in the future, // i.e. how many times in a row the forward button could be pushed. int future_url_count(); private: // Two stacks of strings - these are the only variables you need! // See http://www.cplusplus.com/reference/stack/stack/ for class reference. stack past; stack future; }; #endif 

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

(main.cpp)

#include  #include "browserhistory.h" inline void _test(const char* expression, const char* file, int line) { cerr << "test(" << expression << ") failed in file " << file << ", line " << line << "." << endl; abort(); } #define test(EXPRESSION) ((EXPRESSION) ? (void)0 : _test(#EXPRESSION, __FILE__, __LINE__)) void interactive_mode() { BrowserHistory bh("http://google.com"); cout << "Starting at " << bh.current_url() << "." << endl; cout << "Choose (B)ack, (F)orward, or enter a url to go to." << endl; string line; while (cin) { string line; getline(cin, line); if (line == "B") { if (bh.can_go_back()) { bh.back(); cout << " Now at " << bh.current_url() << endl; } else cout << " Cannot go back." << endl; } else if (line == "F") { if (bh.can_go_forward()) { bh.forward(); cout << " Now at " << bh.current_url() << endl; } else cout << " Cannot go forward." << endl; } else if (line.size() > 0) { bh.go_to_url(line); cout << " Now at " << bh.current_url() << endl; } } exit(0); } int main() { // Uncomment line below to use your BrowserHistory interactively. // // interactive_mode(); // Comments below indicate the current (expected) state of the history. // Example: [url1, url2, url3, (url4), url5, url6] // The urls are listed oldest to newest from left to right, // and the url in parentheses is the current url. // History: [(google.com)] BrowserHistory bh("http://google.com"); test(bh.current_url() == "http://google.com"); test(!bh.can_go_back()); test(!bh.can_go_forward()); test(bh.past_url_count() == 0); test(bh.future_url_count() == 0); bh.go_to_url("http://netflix.com"); bh.go_to_url("http://amazon.com"); bh.go_to_url("http://utrgv.edu"); // History: [google.com, netflix.com, amazon.com, (utrgv.edu)] test(bh.current_url() == "http://utrgv.edu"); test(bh.can_go_back()); test(!bh.can_go_forward()); test(bh.past_url_count() == 3); test(bh.future_url_count() == 0); bh.back(); bh.back(); // History: [google.com, (netflix.com), amazon.com, utrgv.edu] test(bh.current_url() == "http://netflix.com"); test(bh.can_go_back()); test(bh.can_go_forward()); test(bh.past_url_count() == 1); test(bh.future_url_count() == 2); bh.forward(); // History: [google.com, netflix.com, (amazon.com), utrgv.edu] test(bh.current_url() == "http://amazon.com"); test(bh.can_go_back()); test(bh.can_go_forward()); test(bh.past_url_count() == 2); test(bh.future_url_count() == 1); // History: [google.com, netflix.com, amazon.com, (youtube.com)] bh.go_to_url("http://youtube.com"); test(bh.current_url() == "http://youtube.com"); test(bh.can_go_back()); test(!bh.can_go_forward()); test(bh.past_url_count() == 3); test(bh.future_url_count() == 0); bh.forward(); // Can't go forward any more, so do nothing test(bh.current_url() == "http://youtube.com"); bh.back(); bh.back(); bh.back(); // History: [(google.com), netflix.com, amazon.com, youtube.com] test(bh.current_url() == "http://google.com"); bh.back(); // Can't go back any more, so do nothing test(bh.current_url() == "http://google.com"); // Larger test string url("http://url00.com"); for (int i = 0; i < 100; ++i) { url[10] = i / 10 + '0'; url[11] = i % 10 + '0'; bh.go_to_url(url); } // History: [url00.com, url01.com, url02.com, ..., (url99.com)] for (int i = 0; i < 49; ++i) bh.back(); // History: [url00.com, url01.com, ..., (url50.com), ..., url99.com] test(bh.current_url() == "http://url50.com"); cout << "Assignment complete." << endl; }