Mastering Data Structures in C++: Practical Guidelines & Programming Exercises

1. Welcome to Data Structures in C++

2. Course Staff • Teacher : • Ofir Pele • TA: • Teachers of other groups: • Roman Yavich

3. Communications • WWW: moodle • Forums: • Q & A – ask the staff about material. • Exercises forums.

4. Course • ~4 programming exercises • Frontal exam

5. Books & Websites • Books: • A list here: http://www.cprogramming.com/books.html • Recommended for the more advanced stuff: • Scott Meyers “Effective” books (STL, C++). • C++ FAQ – Explaining the complicated stuff, corners etc. • C++ FQA – A bit lot more cynical & pragmatic view of the above

6. Program style

7. Program style • Take the time for it. Very important. If not followed your code will be “write only”. • Common sense • Read “real” coding guidelines document – will give you insight how important it is. e.g. good one from Microsoft or one from Google. • Principles: • Readability • Common Sense • Clarity • Right focus

8. What’s in a name • Example #define ONE 1 #define TEN 10 #define TWENTY 20 • More reasonable #define INPUT_MODE 1 #define INPUT_BUFSIZE 10 #define OUTPUT_BUFSIZE 20

9. What’s in a name • Use descriptive names for global variables • intnpending = 0; // current length of input queue • Naming conventions vary (style) • numPending • num_pending • NumberOfPendingEvents • Be consistent, with yourself and peers.

10. What’s in a name • Consider (wording) intnoOfItemsInQ; intfrontOfTheQueue; intqueueCapacity; … • The word “queue” appears in 3 different ways • Be consistent, with yourself and peers.

11. What’s in a name • Compare for( theElementIndex = 0; theElementIndex < numberOfElements; theElementIndex++ ) elementArray[theElementIndex] = theElementIndex; and for( i = 0; i < nelems; i++ ) elem[i] = i; Use short names for locals

12. What’s in a name Use active name for functions now = getDate() Compare if( checkdigit(c) ) … to if( isdigit(c) ) … Accurate active names makes bugs apparent

13. Indentation Use indentation to show structure Compare for(n++; n <100; field[n++] = 0); c = 0; return ‘\n’; To for( n++; n <100; n++) { field[n] = 0; } c = 0; return ‘\n’;

14. Expressions Use parenthesesto resolve ambiguity Compare • leap_year = y % 4 == 0 && y %100 != 0 || y % 400 == 0; to • leap_year = ((y % 4 == 0) && (y %100 != 0)) || (y % 400 == 0);

15. Statements Use braces to resolve ambiguity Compare • if( i < 100 ) x = i; i++; To • if( i < 100 ) {   x = i; } i++;

16. Idioms Do not try to make code “interesting”! • i = 0; while( i <= n-1 ) { • array[i++] = 1; • }for( i = 0; i < n; ) { • array[i++] = 1; • } • for( i = n; --i >= 0; ) { • array[i] = 1; • }for( i = 0; i < n; i++ ) { • array[i] = 1; • } This is the common “idiom” that any programmer will recognize

17. Idioms Use “else if” for multiway decisions if ( cond1 ) { statement1 } elseif ( cond2 ) { statement2 } … else if ( condn ) { statementn } else { default-statement }

18. Idioms Compare: if( x > 0 ) if( y > 0 ) if( x+y < 100 ) {    ... } elseprintf(Too large!\n" ); elseprintf("y too small!\n"); elseprintf("x too small!\n"); if( x <= 0 ) { printf("x too small!\n"); } elseif( y <= 0 ) { printf("y too small!\n"); }elseif( x+y >= 100 ) {printf("Sum too large!\n" ); }else{   ... }

19. Comments • Don’t write the obvious • // return SUCCESS return SUCCESS; // Initialize total to number_receivedtotal = number_received; • Test: • Does comment add something that is not evident from the code? • Note: “//” Comments are Not Strict ANSI C, but supported by all modern compilers, and clearer in many cases

20. Comments • Don’t comment bad code – rewrite it! • … • // If result = 0 a match was found so return // true; otherwise return false; return !result; • Instead • … • returnmatchfound;

21. Style recap • Descriptive names • Clarity in expressions • Straightforward flow • Readability of code & comments • Consistent conventions & idioms

22. Why Bother? • Good style: • Easy to understand code • Smaller & polished • Makes errors apparent • Sloppy style bad code • Hard to read • Broken flow • Harder to find errors & correct them

23. Note - style in slides: • In the slides we try to follow the style we dictate. • Butdue to space restriction we sometimes bend the rules. • Don’t follow everything you see in the slides.

24. Debugging

25. Debugging 101 • “Define” the bug --- reproduce it • Use debugger and printouts (and other tools e.g. valgrind) • Don’t panic --- think! • Divide & Conquer

26. From C to C++

27. Why C++ is much more fun than C (C++ FAQ)? Classes & methods - OO design Generic programming - Templates allow for code reuse Stricter type system (e.g. function args) Some run-time checks & memory control A common and mature language that gives you high level and low level control Have fun 

28. Why C++ is much more fun than c (C+ FQA)? Tons of corner cases Duplicate features Cryptic syntax Undecidable syntax (uncompilableprogarms!) No two compilers agree on it Probably one of the hardest computer languages to master. Have fun 

29. History tr1: library additions ('05) auto, lambdas, threading,… Practically current c++ Minor changes Major compilers: Latest versions are starting to implement features from c++11 (prev. c++0x) approved draft

30. Course Objectives • Learn the language • Practice of programming data structures • Design • Testing & Debugging • Efficiency & Portability • Modularity

31. Course structure

32. First Program in C++ • // This line includes the standard // I/O library file (similar to “copy here this file”) #include<iostream>int main() {    std::cout << "Hello class!\n"; return0; }

33. Compiling & Running… • Visual Studio… • In Linux: • > g++ –Wall hello.cpp –o hello • > hello • Hello class! • >

34. The missing types Fill in missing types from C, in somewhat crude way

35. strings in C++ • #include<iostream>#include<string>int main() {    std::stringstr; int a; double b;    std::cin >> str >> a >> b; if(std::cin.fail())    {       std::cerr << "input problem\n"; return1;    }    std::cout << "I got: "<< str << ' '   << a << ' ' << b << std::endl; } More about string functions: http://www.cppreference.com/cppstring

36. Boolean variables • #include<iostream>int main() { int a = 5; boolisZero = (a == 0); • // same conditions if(!isZero && isZero==false && isZero!=true && !!! isZero && a ) {       std::cout << "a is not zero\n";    } }

37. Enum (C)

38. User Defined Type - enum • Enumerated data - a set of named constants. • Usage: enum [identifier]{enumerator list} enumSeason { WINTER, // = 0 by default SPRING, // = WINTER + 1 SUMMER, // = WINTER + 2 AUTUMN// = WINTER + 3}; enum {SUNDAY=1, MONDAY, TUESDAY, …}; // nameless enumColor {BLACK,RED,GREEN,YELLOW,BLUE,WHITE=7,GRAY}; // 0 1 2 3 4 7 8

39. enum enumSeason { WINTER, // = 0 by default SPRING, // = WINTER + 1 SUMMER, // = WINTER + 2 AUTUMN// = WINTER + 3}; enumSeason curr_season;curr_season= AUTUMN; curr_season= 19;// legal, but ugly, g++: warning intSUMMER; // error, redefinitionintprev_season = SUMMER; // legal, but ugly, g++ warning

40. Use enum to eliminate magic numbers – alternative to #define

41. C++-11 enum class enumclassSeason : char{ WINTER, // = 0 by default SPRING, // = WINTER + 1 SUMMER, // = WINTER + 2 AUTUMN // = WINTER + 3}; Season curr_season;curr_season= Season::AUTUMN; curr_season= SUMMER; // won’t compile! curr_season= 19; // won’t compile! intprev_season= Season::SUMMER; // won’t compile!

42. enums – why? • More readable code • Code less error prone • Accessible for debugger • Use of the numerical values is not disabled • bad programming usually!

43. Overloading Understand and remember. More than syntactic sugar. This is how a lot of stuff works under the hood (e.g. inheritance)

44. Function overloading - C • #include<stdio.h>void foo() { printf ("foo()\n"); } void foo(int n) { printf ("foo(%d)\n", n); } int main() {    foo(12);    foo(); return0; } Compilation output: Error: Multiple definition of foo

45. Function overloading – C++ • #include<iostream>void foo() {    std::cout << "foo()\n"; } void foo(int n) {    std::cout<<"foo("<<n<<")\n"; } int main() {    foo(12);    foo(); } Output: Compile, and print: foo(12) foo()

46. Default parameters • #include<iostream>void foo(int n=5) {    std::cout << n; } int main() {       foo(); } Output: Compile, and print: foo(5)

47. Overload resolution • Find all functions with same name “candidates”. Let’s call them • Find which have the correct number of arguments - “viable candidates” • Find with best matching arguments. • if • use that function. • else (0 or more than 1): • emit compilation error.

48. Memory & Arrays (C)

49. Memory • int main() { char c; int i,j; double x; c i j x

50. Arrays • Defines a block of consecutive cells • int main() { int i; int a[3];   i a[0] a[1] a[2]