CSC 107 – Programming For Science

Announcements  Tutors available MTWR in WTC206/WTC208  Special lab (with Macs) & not in the Tutoring Center  Can answer questions you have about material  Also very good at helping with weekly assignments  Directly across from my office, so I can also help  My office hours are minimum time I am around  During the day, often (usually) around at other times  Please ask questions and get any help you need  No RSVPs; could also take candy I have in my office

Today’s Goals  Be able to use if – else if – else statements  Know how to order choices to work properly  Explain why if & else if conditions not related  Correctly use braces ( { } ) and make code pretty  Explain when & why if – else if – else used

if (…) statement  1 st evaluates boolean expression in parenthesis  Executes next statement if expression is true  When expression is false, skips over the statement int num = -32; if (num > val; if ((val < num) || (val <= 0)) { cout << "That was a poor choice“ << endl; }

if (…) statement

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 ifelse  In these cases, can use if-else statement must  else must come 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 having if & no else false true

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; }

Many Choices  May want to choose from many possibilities

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; } } }

Many Choices  May want to choose from many possibilities  Could nest if – else statements inside one another else if  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; }

if – else if – else Usage

if – else if – else Example if (wealth > ) { cout ) { cout ) { cout 10000) { cout 0) { cout << "Good luck" << endl; }

if – else if – else Example if (wealth > ) { cout ) { cout ) { cout 10000) { cout 0) { cout << "Good luck" << endl; }

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

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

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

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

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  If line could or does contain { add to indentation  Decrease indentation each } should be on a line  if, else if, or else line has opening brace  Always use braces to prevent having to fix bugs  Save space: closing brace on else/else if line  Closing brace on own line at end of the statement

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

Coding Style Example #include using namespace std; int main() { int dcScore = 22, azScore = 21; if (dcScore > azScore) { cout << "Prof. Hertz happy" << endl; cout << "His team won" << endl; } else { cout << "His team lost." << endl; cout << "He gives out Fs"; dcScore += 100; if (dcScore < azScore) { cout << "Ouch. That's Buffalo bad." <<endl; } } cout << "And now code continues" << endl; return 0; }

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

For Next Lecture  Read sections 7.4, 7.6 – 7.7 for Friday  What if we want to run multiple clauses?  Is something easier for testing lots of equality?  How can we break lots of things?  Week #3 weekly assignment due yesterday  But could still submit today by using virtual extension  Week #4 weekly assignment also on Angel  If problem takes more than 10 minutes, TALK TO ME!