Boolean != Spooky Dance

Posted by Tam Vu on October 6, 2018

Booleans….intial thoughts on the word: “boo” = something spooky…“lean” = slim…maybe tilting the body…like a dance (Now lean back, lean back, lean back, lean back).. Turns out, it has nothing to do with scary dances or lean ground beef.

Quick google and it turns out boolean actually comes from the man who invented Boolean Logic in the 19th century – George Boole. Thanks to this guy, true/false logic was brought to the programming world.

Boolean Cheat Sheet ( does it pretty well, but I’ll try to simplify it even more)

2 key points to keep in mind:

  • ”=” is to set a variable; “==” is for equalities
  • ”!” reverses the logical state; for example, “!=” is read as “not equals”

Boolean operators:

  • “&&” (“and” ) - both values of either side must be true to evaluate true
  •   ” (“or”) - only one value on either side must be true to evaluate true

Example lab completed with booleans

Objective: in order for the move to be valid, it must be on the board and the position can’t be taken Thinking process:

  • must be between indexes 0-8. So “index.between?(0.,8)
  • should use an && because two conditions have to be true
  • already created #position_taken…it evaluates true if the position is taken…but for #valid_move, I need the position to be empty…
  • use the ! to reverse #position_taken; in a sense, changed position_taken to position not taken
  • okay lets put it all together:
def valid_move?(board, index)
  index.between?(0,8) && !position_taken?(board, index) 

Boom, it worked. Basic boolean logic at its finest.