Episode 003: Tic-Tac-REPL

Nate tries to turn the tic-tac-toe "game engine" into a real application he can play with a friend.

• Let's play the game!
• How do you keep track of the game state as it changes?
• Bucket brigade the reference to the future loop using recur
• The game loop: read input, evaluate, print out new board, loop.
• "It has occurred to me that we are basically writing a REPL."
• "We have the tic-tac-REPL"
• How do you get input from the user? How to you make sure it's right?
• "It keeps harassing the non-compliment user until they type the right thing in"
• Input loop: read, validate, loop on error, return on success
• Keep the logic pure! Separate out the parsing and validation functions.
• "Much better to tuck it away in a function!"
• Sequence the pure parts with a minimalist function that does the I/O.
• "I don't like having ovens present because they're hard to put in my test cases."
• Unit test those pure parts. (No one likes to be mocked.)
• I/O is a side effect!
• "Every time I redefine one of those things I feel like I'm reaching down into the bowels of Clojure and doing something moderately illegal."
• Using keywords as error codes is nifty
• "You don't have any different kinds of nil. You just have one. It's the nuh-uh."
• Can use a tuple with the first element always being a keyword and the second being data for the "details"

Clojure in this episode:

• read-line
• string/split
• swap! and reset!
• loop and recur
• let vs loop
• keywords
• nil punning