CVS

Admistrivia

• Most everyone got things to run
• Problems included:
  • incorrect perl address (hint: copy from my directory)
  • permissions to tight (public can't read)
  • permissions to lose (public can write)
  • DOS file format (looking for the program /usr/bin/perl)
  • Can't run from command line (any problem in code does this)
  • Believing in a consistent world view (putting &le and &gr around html header)

CVS

• logical programming vs experimental programming
  • logical approach: use designed languages say ML, smalltalk
  • For all others, use experimental approach
  • Logical can be done with pencil and paper (some schools actually teach this way)
  • experimental requires running lots of code
• Experimental programming methods
  • Just like any other controled experiment
  • sample size requirements aren't as high as for drug testing
  • BUT, you do need to do controlled experiments
• Primary tool of controlled experiment is a version control system
  • Problem: there is more than one experiment you can do
    • say running from the command line
    • running on sample input
    • running from web
    • checking colors
  • If you make a whole bunch of changes without running ALL of your tests, you will find yourself with broken code
  • you undo those changes to make a clean experiment
  • CVS allows unlimited undo's
• Picture of cvs tree (yikes! Do we really need all of that?) (names: head, branch, tags, version number.)
• Picture of single user cvs thread (ah, that makes more sense)
• How to see the thread?
  • Find a cvs gui (only for people born after 1980)
  • The real way: use cvs commands
  • "cvs log" shows tree
  • "cvs diff" shows what has changed
  • "cvs co -r1.4" rolls back to some previous time
• Rules of experimental programming using CVS
  • Check in frequently. Write comments every time. (To get your comments to appear in your file put in the statement $log:$ into your file.)
  • Start with simple working code (say hello world)
  • Gradually modify that code to do what you want it to do
  • When you discover it no longer works on the web, roll back until it runs on the web
  • Now look and see what you changed. it should only be about 5 lines. figure out what went wrong in those 5 lines. Patch them into the head.
  • Check that the head works, and check it in.
• Class rules:

  If you have problems with your code, tell me between which versions the problem started. There should only be a few lines of difference. Email me the "cvs diff -r1.5 -r1.6" output and I'll see if I can figure out the problem.