4.3. Alternative Execution

A second form of conditional execution is alternative execution, in which there are two possibilities, and the condition determines which one gets executed. The syntax looks like:

if (x % 2 == 0)
{
  cout << "x is even\n";
}
else
{
  cout << "x is odd\n";
}

If the remainder when x is divided by 2 is zero, then we know that x is even, and this code displays a message to that effect. If the condition is false, the second set of statements is executed. Since the condition must be true or false, exactly one of the alternatives will be executed.

As an aside, if you think you might want to check the parity (evenness or oddness) of numbers often, you might want to “wrap” this code up in a function, as follows:

void print_parity (int x) {
  if (x % 2 == 0)
  {
    cout << "x is even\n";
  }
  else
  {
    cout << "x is odd\n";
  }
}

Now you have a function named print_parity that will display an appropriate message for any integer you care to provide. In main you would call this function as follows:

print_parity (17);

Always remember that when you call a function, you do not have to declare the types of the arguments you provide. C++ can figure out what type they are. You should resist the temptation to write things like:

int number = 17;
print_parity (int number);         // WRONG!!!

This program shows you how the print parity function works. Feel free to modify the values of number and other to see how the output is changed.

#include <iostream> using std::cout; void print_parity (int x) { if (x % 2 == 0) { cout << "x is even\n"; } else { cout << "x is odd\n"; } } int main () { int number = 17; print_parity(number); number = 18; print_parity(number); }

Q-2: What will be printed after the main is executed?

void weather(int temp) {
  if (temp < 52)
  {
    cout << "It is cold!";
  }
  else
  {
    cout << "It is warm!";
  }
}

int main() {
  int degrees = 52;
  weather(degrees);
}

• It is cold!
• That statement would print if degrees was less than 50.
• It is warm!
• Correct!
• Nothing prints.
• One of the statements is satisfied, so something does print.
• Error message.
• There is nothing in the code below that would generate an error.

Construct a block of code that correctly goes through alternative execution for pricing of an entre at a nice restaurant. If the price is more than $30.00, print “Expensive!”. If the price is less than $30.00, print “Inexpensive!” You should by initializing the cost to $40.

        int cost = 40;

if (cost > 30) {

if (cost > 30) #distractor

 cout << "Expensive!";

} //"if" bracket

else {

else if { #distractor

 cout << "Inexpensive!" #distractor

 cout << "Inexpensive!";

} //"else" bracket
        

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More to Explore

• if and comparison operators from cppreference.com

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