loops

Loops

Creating Loops Easily

• Start with one case
• Write pseudocode in comments
• Code case with literals
• Indent it, and put a loop around it
• Replace literals with:
  • loop indexes
  • computed expressions
• Replace more literals
• Repeat as many times as needed

Avoiding Problems

• Minimize the number of factors affecting the loop
• Treat inside of the loop as if it were a routine
  • Surrounding program knows the control conditions but not the contents
• Make loop termination obvious
• Dont have code that depends on a loop indexes final value
• Limit nesting to 3 levels

Types of Loops

While Loops

• Flexible - use when unknown how many times will execute
• Two types:
  • Test at the beginning
  • Test at the end

For Loops

• Rigid - use when known how many times need to execute
• Good for simple activities that dont require internal loop controls

Testing Loops

• Care about three cases of interest
  • The first case
  • An arbitrary middle case
  • The last case
• CHECK ALL OF THESE