CIS 150 Selection

• solve problems using C++ selection
• use C++ if statements
• use C++ if/else statements
• use C++ nested if/else statements
• use the C++ conditional operator (if time permits)
• use C++ switch statements (if time permits)
• validate user input (very basic validation)

Remember that these topics are covered well in the text. These notes are just an outline for classroom discussion/lecture.

• if statement - used for single-branched selection if (condition) { statement(s) // executed if condition is true }
• if/else - used for two-branched selection if (condition) { statement(s) // executed if condition is true } else { statement(s) // executed if condition is false }
• nested if/else - used for complex selection if (condition1) { statement(s) // executed if condition1 is true if (condition2) { statement(s) // executed if condition1 AND condition2 are true } else { statement(s) // executed if condition1 is true but condition2 is false } } else { statement(s) // executed if condition1 is false }
• switch switch (intExpression) { case value1: statement(s) // executed if intExpression == value1 break; case value2: statement(s) // executed if intExpression == value2 break; default: statement(s) // executed if no values matched intExpression }
• conditional operator (?:)
• see testsel1.cpp for "if" demonstration
• see testsel2.cpp for "if/else" demonstration
• see testsel3.cpp for "if/else" range checking
• see testsel4.cpp for "switch" demonstration
• see testsel5.cpp for "?:" demonstration, calculates maximum value

• only ternary operator
• operates like an inline if/else
• expr1 ? expr2 : expr3
  if expr1 is true, the whole thing is replaced by expr2,
  otherwise it is replaced by expr3
• grossPay = hours>40 ? rate*40 + (hours-40)*rate*1.5 : hours*rate;

• allows branching based on equality to integral values
• less flexible then if/else, but useful for certain situations which have a very limited number of input values (such as menu selections)
• if statements easily handle ranges of values (such as hours > 40, or age > 21 && age < 40), but switch statements do not
• switch (option) { case 1: cout << "Loading from file\n"; break; case 2: cout << "Saving to file\n"; break; case 3: cout << "Printing report\n"; break; case 4: cout << "Terminating program\n"; break; default: cout << "Invalid choice\n"; }

• data validation makes use of the selection structures we have just covered
• see testio2.cpp for data validation using if/else
• see testio3.cpp for data validation using switch

• calcpay1.cpp: if/else demo
• calcpay2.cpp: if/else and output formatting demo
• calcpay3.cpp: single-branch "if" demo
• testmenu1.cpp: menuing using nested if/else
• testmenu2.cpp: menuing using streamlined nested if/else
• testmenu3.cpp: menuing using switch statement
• testmenu4.cpp: menuing using switch and input validation