Class 22: Control Flow: Miscellaneous

Held: Tuesday, 1 March 2011

Summary: We continue to consider loops in C, trying not to break our understanding.

Related Pages:

• EBoard.
• Lab: Loops in C.
• Reading: K&R 3.7-3.8.

Notes:

• New partners! (This will be the last week that you are required to select new partners.)
• I'll reserve time at the start of class for questions on Assignment 5.
• I've posted some answers to your questions on the control flow reading.
• Questions on loops reading missing from: AG, MH, AH, JJ, JTL, BW, BZ.
• Tonight's reading: K&R 4.1-4.3.
• EC: Thursday's CS Extra: FPGAs.
• EC: Friday's CS Table: GPU programming in CUDA, revisited.

Overview:

• Modifying loop control.
• More extreme modifications with goto.
• Lab.

Modifying Control with break and continue

• Two new ways to affect the behavior of loops
  • break - exit the loop now!
  • continue - skip the rest of the body.
• Normally used with a conditional
• None is necessary.
  • continue can be handled by an if.
  • break can be handled with a sentinel and a continue

Extreme Modifications to Control: goto

• You can label parts of your code with a name and a colon.
• You can then jump to that part of your code with goto.
• Goto was one of the first control structures invented, and it handles most forms of looping (although some recursive procedures are hard to write with goto).
• Unconstrained use of goto leads to unreadable code.
  • Goto considered harmful was a famous paper in CS.

Lab

• Do the lab.
• Be prepared to reflect.