Nested if

• The statements inside of an if statement can be if statements.

  if ('y' == answer or 'Y' == answer) {
      if (hoursWorked > 40) {
         ...
      } else {
         ...
      }
       
  } else {
      ...
  }
      

• Without brackets and indentation this becomes very hard to follow
• If it is too deep it becomes very hard to follow.
• You should limit to no more than two to three levels deep.
• Write a program which plays paper-scissors-rock: It should ask what the first and second player selected and print the winner of if it is a tie.

  •         get player 1 choice
    	get player 2 choice
    
    	if player1 is paper
    	   if player 2 is paper
    	       print tie
    	   else
    	       if player 2 is scissors
    	           print player 2 wins
                   else 
    	           if player2 is rock
    		      print player1 wins
            else 
    	...
        

  • psrBad.C
• We could do some things to fix this:
  • Check for bad input BEFORE we start testing for a winner
    • This is probably good anyway, since we will learn how to go back and ask for new input next chapter.
    • And it reduces the complexity of the mondo if statement.
  • Check for a tie before the modo if statement.
  • psrBetter.C
• If we are breaking something up into different classes we can do better yet.
  • C++ does not have an else-if statement.
  • But we can build one

    if (exp1) {
       statements;
    } else if (exp2) {
       statements;
    } else if (exp3) {
       statements;
    ...
    } else {
       statements;
    }
    	

  • psrGood.C
• Write a program, which give the day number (0=Sunday... 6=Saturday) prints the name of the day of the week. Print "invalid" if the number is not valid.