The DO/While and For loops

• There are two additional loops in C
• The for loop.
  • This loop reminds us of what we need to do to construct a valid loop.

  •  for(init statement; boolean expression; increment statement) 
         body statement
             

  • Semantics:
    1. execute the init-statement
    2. evaluate the boolean expression
    3. if the boolean expression is false, exit the loop
    4. execute the body statement
    5. execute the increment statement
    6. return to step 2.
  • This is just a special case of a while loop

    init statement
    while (boolean expression)  {
        body statement
        increment statement
    }
    	 

  • example:
    for(i=0; i < 10; i++) { cout << i << endl; }
  • The book tells us that this is for counter-controlled loops, but I disagree.
  • I like this statement, it reminds me to do all of the things to make a successful loop.
  • Caution: , is not a ;
    • for(i=3, j=8; i!=j; i++,j--) is legit, but bad
  • Any statement in the () can be left blank.
    • for(;;) is an infinite loop.
    • for(goodData = false; !goodData;) might be an input loop
  • Declaring the lcv in the for statement
    • for (int i=0; ...)
    • i is valid only inside of the for loop.
    • This is not the best idea
    • But you do see it.
• The Do-While loop
  • do statement; while(boolean expression)
  • Semantics
    1. execute the statement
    2. evaluate the boolean expression
    3. If the boolean expression is true, return to step 1.

  • do {
       statements;
    } while (boolean expression)
    	

  • This is really a specialized while loop

    loop body
    while (boolean expression)
       loop body
    	

  • I mostly use this for a menu.
  • I use this very infrequently.