1. CSC 107 – Programming For Science

2. Spacing in a Program  C++ ignores spaces in a program  This also means where newlines placed ignored  #define & text in quotes major exceptions to rule  This can lead to interesting code choices

3. Coding Style  Use consistent size to indent (I use 2 spaces)  Not required, but makes it much easier to read code  Indent code within braces ( {} ) to show structure  Code could/does contain { add to indentation  Decrease indentation each } that found in the code  if, else if, or else line has opening brace  Always use braces to prevent having to fix bugs  Limit space, closing brace on else/else if line  Closing brace on own line otherwise (like at end)

4. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

5. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

6. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

7. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

8. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

9. Coding Style Example #include using namespace std; int main(void) { int dcScore = 23, nycScore = 26; if (dcScore > nycScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He is sad"; dcScore += 100; if (dcScore < nycScore) { cout << "Ouch. That's bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

10. if (…) statement  Parenthesis first, evaluate this expression  Execute next statement, when expression true  When expression is false, skips over statement int nyc = 32, dc = 1; bool gang = (nyc > 12) && (dc == 1); if (nyc >= dc) { cout << “You lie" << endl; } if (!gang) { cout << "That ain't right." << endl; }

11. I Want More!  Add opening brace ( { ) after closing parenthesis  Can now write all statements to execute  Add closing brace ( } ) to show where block ends  If expression false, execution restarts at that point if (sqrt(x) == 3.0) { someVar = 45 + 65 * 12; cout << "root of x = 3" << endl; cout << "So, x = 9" << endl; }

12. else statement  Often want to perform one of two actions  Execute some statements when condition is true  But when it is false, do some other work  Continue as normal afterward, no matter the path  In these cases, can use if-else statement  else comes immediately after if 's ; or }  Like if, else should always have {}  Cannot have else without if to start process  In C++, there is no problem with if & no else yesno

13. if - else Examples if (value > 0) { cout << "Its positive" << endl; } else { value = abs(value); } if ((year % 4 == 0) && ((year % 100) != 0)) { daysInYear = 366; cout << "Not quite right, but close enough"; cout << endl; leapYear = true; } else { leapYear = false; daysInYear = 365; }

14. Many Choices  May want to choose from many possibilities

15. Many Choices  May want to choose from many possibilities  Could nest if – else statements inside one another if (a > 3) { cout 10) { cout << "b greater than 10" << endl; } else { if (c == -23) { cout << "c is equal to -23" << endl; } else { cout << "This really sucks" << endl; cout << "Sorry its stupid" << endl; } } }

16. Many Choices  May want to choose from many possibilities  Could nest if – else statements inside one another  Or easier & nicer if – else if – else statement if (a > 3) { cout 10) { cout << "b greater than 10" << endl; } else if (c == -23) { cout << "c is equal to -23" << endl; } else { cout << "This really sucks" << endl; cout << "Sorry its stupid" << endl; }

17. if – else if – else Usage  Must begin with if statement at the start  This is required; what would we be saying else to?  Only  Only required part of this entire process  Can then have zero or more else if s  Tests can be anything; do not have to be related  Until one is true, will be examined one-by-one  Execute 1 st clause where true expression is found  Only at the very end can have else clause  If nothing else matches then else is executed

18. if – else if – else Example if (wealth > 1000000) { cout 100000) { cout -100000) { cout 10000) { cout 0) { cout << "Good luck" << endl; }

19. if – else if – else Example if (wealth > 1000000) { cout 100000) { cout -100000) { cout 10000) { cout 0) { cout << "Good luck" << endl; }

20. if – else if – else Example if (wealth > 1000000) { cout 100000) { cout -100000) { cout 10000) { cout 0) { cout << "Good luck" << endl; } else { cout << "Government bailout!" << endl; }

21. if – else if – else Example if (wealth > 1000000) { cout 100000) { cout -100000) { cout 10000) { cout 0) { cout << "Good luck" << endl; } else { cout << "Government bailout!" << endl; }

22. if – else if – else Example if (wealth > 1000000) { cout 100000) { cout 10000) { cout 0) { cout -100000) { cout << "File for bankruptcy" << endl; } else { cout << "Government bailout!" << endl; }

23. Your Turn  Get in groups of 3 & work on following activity

24. For Next Lecture  Read sections 7.4, 7.6 – 7.7 for Wednesday  What if we want to run multiple clauses?  Is something easier for testing lots of equality?  How can we break lots of things?  Week #4 weekly assignment available now  Problems available on Angel  If problem takes more than 10 minutes, TALK TO ME!