CSC102 INTRO TO PROGRAMMING WITH PYTHON LECTURE 28 OOPS IN C++ MICHAEL GROSSBERG

Transcription

1 CSC102 INTRO TO PROGRAMMING WITH PYTHON LECTURE 28 OOPS IN C++ MICHAEL GROSSBERG

2 FUNCTION OVERLOADING int f(int) double f(double) double f(double,int) string f(string) CALLS THE FUNCTION BASED ON WHAT IS PASSED TO IT

3 FUNCTION OVERLOADING UNLIKE PYTHON FUNCTION MUST TAKE THE RIGHT TYPE OR IT WON T EVEN CALL IT #include <iostream> using namespace std; int twice(int x) return (x+x); string twice(string x) return (x+x); int main() cout << twice(5) << endl; cout << twice(string("soup")) << endl; PROBLEM: REPEATING SAME CODE FOR EACH TYPE

4 TEMPLATES PARAMETERIZED TYPES S f(t) WHEN YOU WANT TO DO THE SAME THING FOR LOTS OF SIMILAR TYPES COMPILES COPY OF CODE FOR EACH TYPE YOU ACTUALLY USE

5 TEMPLATES #include <iostream> using namespace std; template<class T> T twice(t x) return (x+x); int main() cout << twice(5) << endl; cout << twice(string("soup")) << endl; DECLARE THAT T WILL BE A TEMPLATE USE TEMPLATE AS IF IT WERE A TYPE IF THIS IS ILLEGAL IT FIGURES THIS OUT WHEN IT TRYS TO MAKE AN INT AND STRING VERSION

6 GENERATING RANDOM NUMBERS #include <iostream> #include <cstdlib> using namespace std; int rand_int(int,int); int main() srand( time(null) ); for(int i = 0; i < 20; i++ ) printf( "Random number #%d: %d\n", i, rand_int(1,11)); int rand_int(int rand_min=0,int rand_max=rand_max) int range = rand_max-rand_min; return rand_min + (rand()%range); YOU WILL MISS SOME PYTHON LIBRARIES

7 ARRAY ARRAYS CAN HOLD ANYTHING const int ARRAY_SIZE = 20; int num_array[array_size]; TOTAL SIZE FIXED FILL ONLY PART

8 LIKE PRIMITIVE LISTS #include <iostream> #include <cstdlib> using namespace std; int main() const int ARRAY_SIZE = 20; int num_array[array_size]; srand( time(null) ); printf("array probably has junk in it.") for(int i = 0; i < ARRAY_SIZE; i++ ) printf( "num_array[%d]= %d\n", i, num_array[i]); //Always should clear it like this for(int i = 0; i < ARRAY_SIZE; i++ ) num_array[i]=0; GET ELEMENTS LIKE PYTHON LIST SET ELEMENTS LIKE PYTHON LIST ALWAYS CLEAR VARIABLES FIRST

9 OFF THE DEEP END #include <iostream> using namespace std; const int JUNK_NUM = ; void init_array(int [],int); int main() const int ARRAY_SIZE = 20; int num_array[array_size]; init_array(num_array,array_size); srand( time(null) ); // indexing past the end for(int i = ARRAY_SIZE-2; i < ARRAY_SIZE+1; i++ ) printf( "num_array[%d]= %d\n", i, num_array[i]); // This is SO wrong void init_array(int num_array[], int size) for(int i = 0; i < size; i++ ) num_array[i]=junk_num; TRICK: ALWAYS INITIALIZE WITH A EASY TO SPOT VALUE HUGE SECURITY PROBLEM PAST THE END!!!!!

10 VECTOR WORKS LIKE LIST #include <vector> vector<int> num_vect; THE VECTOR LIBRARY A VECTOR num_vect.push_back(9) num_vect[i] num_vect[i] = 7 YOU CAN READ PAST THE END AUTO RESIZE CAN GET SIZE CAN LOAD UP NEW ELEMENTS GET LIKE ARRAY SET LIKE ARRAY

11 #include <iostream> VECTOR WORKS LIKE LIST #include <cstdlib> #include <vector> #include <string> #include <sstream> using namespace std; string vect2string(vector<int> &); int rand_int(int,int); int main() const int VECT_SIZE = 20; vector<int> num_vect; int rand_num = 0; srand( time(null) ); cout << "num_vect = ["; cout << vect2string(num_vect) << "]" << endl; for (int i=0;i<vect_size;i++) rand_num = rand_int(0,11); //cout << "rand_num = " << rand_num<< endl; num_vect.push_back(rand_num); cout << "num_vect = ["; cout << vect2string(num_vect) << "]" << endl;

12 VECTOR2STRING (C++ STYLE) LIKE COUT ONLY PIPE GOES TO HOLDING TANK string vect2string(vector<int> &num_vect) string result=""; stringstream out; for(int i=0;i<num_vect.size();i++) out<<num_vect[i]; if ((1<num_vect.size())&&(i< (num_vect.size()-1))) out<<", "; return out.str(); FILL IT UP EMPTY IT OUT

13 CLASS POINT #include <iostream> using namespace std; class Point double x; double y; public: Point(double,double); double get_x() constreturn x; void set_x(double in_x)x=in_x; double get_y() constreturn y; void set_y(double in_y)y=in_y; ; Point::Point(double in_x=1,double in_y=1) x=in_x; y=in_y; return; ATTRIBUTES AND METHODS PRIVATE BY DEFAULT MAKE PUBLIC FOR OUTSIDE USE int main() Point p; cout << "p=(" << p.get_x()<< ", "<< p.get_y()<< ")\n"; p.set_x(7); p.set_y(.5); cout << "p=(" << p.get_x()<< ", "<< p.get_y()<< ")\n"; SETTERS/GETTERS DECLARE IMPLEMENT USE. TO ACCESS METHOD

14 C++ OPERATOR OVERLOADING int main() Point p; Point q; cout << "p=" << p << endl; q = p+p; cout << "p=" << q << endl; OVERLOAD + OVERLOAD COUT <<

15 OVERLOADING + #include <iostream> using namespace std; class Point... public: Point(double,double); Point operator+(point const&);... DECLARE IMPLEMENT ; Point Point::operator+ (Point const& other) Point sum = Point(x+other.get_x(),y+other.get_y()); return sum;

16 COUT << MYCLASS LIKE PYTHON STR METHOD BUT ostream& operator<<(ostream& os, Point& point) os << "(" << point.get_x() << ", "; os << point.get_y() << ")"; return os; NOT A CLASS METHOD... JUST OVERLOADING <<

17 CARDS.PY -> CARDS.CPP LENGTH C LINES OF CODE VS PYTHON 113 LINES OF CODE COMPLEXITY C++: MUCH MORE BOILER PLATE MUST BE VERY CAREFUL WITH CONST AND REFRENCES

18 #include <iostream> cards.push_back(in_cards[ind]); ; #include <string> Deck::Deck() #include <vector> bool Card::operator== (Card const& card) const ; for (int ind=0; ind < NUM_RANKS; ind++) #include <cassert> return (rank == card.rank); CardStack::CardStack(); for (int jnd=0; jnd < NUM_SUITS; jnd++) #include <iostream> cards.push_back(card(ind,jnd)); #include <algorithm> bool Card::operator!= (Card const& card) const CardStack CardStack::deal(int num_cards=2) using namespace std; return (rank!= card.rank); vector <Card> temp_cards; namespace cards for(int ind=0; ind < num_cards; ind++) ; const int NUM_SUITS = 4; bool Card::operator< (Card const& card) const temp_cards.push_back(cards[cards.size()-1-ind]); ; const string suits[] = "Clubs", "Diamonds", "Hearts", return (rank < card.rank); using namespace cards; "Spades"; for(int ind=0; ind < num_cards; ind++) int main () const int NUM_RANKS = 13; const string ranks[] = "Ace", "2", "3", "4", "5", "6", "7", "8", "9", "10", "Jack", "Queen", "King"; class Card int suit,rank; public: Card(int,int); string get_suit()return suits[suit];; string get_rank()return ranks[rank];; int value(); bool Card::operator<= (Card const& card) const cards.pop_back(); return (rank <= card.rank); A LOT OF CODE return CardStack(temp_cards); bool Card::operator> (Card const& card) const ; SAME return (rank > card.rank); FUNCTIONALITY void CardStack::sort() std::sort(cards.begin(),cards.end()); bool Card::operator>= (Card const& card) const ; MUCH HARDER TO MANAGE return (rank >= card.rank); void CardStack::shuffle() for(int ind = 0;ind < 7; ind++) ostream& operator<<(ostream& os, Card& card) std::random_shuffle(cards.begin(),cards.end()); vector <Card> my_cards; Card card(0,0); my_cards.push_back(card); Card card1(0,0); my_cards.push_back(card1); Card card2(1,1); my_cards.push_back(card2); CardStack stack(my_cards); stack.toostream(cout); bool operator== (Card const&) const; stack.sort(); bool operator!= (Card const&) const; os << card.get_rank() << " of " << card.get_suit(); ; stack.toostream(cout); bool operator< (Card const&) const; return os; CardStack CardStack::operator+(CardStack const& other) stack.shuffle(); bool operator<= (Card const&) const; vector <Card> temp_cards; stack.toostream(cout); bool operator> (Card const&) const; class CardStack for(int ind=0; ind < cards.size(); ind++) CardStack stack2(my_cards); bool operator>= (Card const&) const; protected: temp_cards.push_back(cards[ind]); stack2 = stack+stack; ; vector <Card> cards; stack2.toostream(cout); Card::Card (int r,int s) public: for(int ind=0; ind < other.cards.size(); ind++) cout << card ; assert(0<=r); CardStack(); temp_cards.push_back(other.cards[ind]); cout << endl; assert(r<13); CardStack(vector <Card> const&); cout << (card1==card) << endl; assert(0<=s); int size(); return CardStack(temp_cards); cout << (card2==card)<< endl; assert(s<4); ostream& toostream(ostream& os); ; Deck deck; rank=r; void sort(); ostream& CardStack::toOstream(ostream& os) cout << "Deck: "; suit=s; void shuffle(); deck.toostream(cout); ; CardStack deal(int); for (int ind=0; ind < cards.size();ind++) cout << endl << endl; int Card::value() CardStack operator+(cardstack const&); os << cards[ind]<< endl; deck.shuffle(); if (0==rank) ; deck.toostream(cout); return 11; int CardStack::size() return os; cout << endl << endl; else if (rank>9) return cards.size(); ; cout << "Hello World! "; // prints Hello World! return 10; class Deck:public CardStack cout << "I'm a C++ program\n\n"; // prints I'm a C++ program else CardStack::CardStack(vector <Card> const& in_cards) public: return 0; return rank+1; for (int ind=0;ind < in_cards.size();ind++) Deck();

19 PYTHON -> C++/JAVA/C# CODE FIRST IN PYTHON TO UNDERSTAND PROBLEM RECODE IN TARGET LANGUAGE RAPID PROTOTYPING

20 EXTENDING PYTHON CODE FIRST IN PYTHON DETERMINE WHERE PROGRAM IS SLOW WHERE WOULD C++/JAVA/C# LIBRARY HELP CALL FROM INSIDE PYTHON C++: USE WEAVE, BOOST, SIP, SWIG JAVA: USE JYTHON C#: USE IRON PYTHON

21 EMBEDDING PYTHON SOMETIMES YOU WANT PYTHON TO RUN INSIDE C++ EMBED EXAMPLE: BUILD A COMPLEX PROGRAM WANT TO INCLUDE AN INTERACTIVE SHELL WOULDN T THAT BE COOL IN PHOTOSHOP?

22 THANKS