## day 3

Today’s goal is to finish up the basic feature of Tetrix so it’s playable.

### REPL

A few people in the community is coming up with best practices in Scala.

As you would expect all of them mention to “Favor Immutability” and “Use None instead of null” like Programming in Scala book. Some of the notable ones are “Know Your Collections” and “Consider Always Providing Return Types on Functions and Methods” by Venners/Wall, and more recently “Experiment in the REPL” by Josh.

Experiment-driven development is where you, the developer, first spend some time experimenting with a live interpreter or REPL before writing tests or production code.

From the sbt shell, you can run `console` to get into the RELP which automatically loads your code into the classpath. Let’s try to create the setup for clearing the bottom row:

``````> console

Welcome to Scala version 2.9.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_33).
Type in expressions to have them evaluated.

scala> import com.eed3si9n.tetrix._
import com.eed3si9n.tetrix._

scala> import Stage._
import Stage._

scala> val s3 = newState(Seq(
|     (0, 0), (1, 0), (2, 0), (3, 0), (7, 0), (8, 0), (9, 0))
|   map { Block(_, TKind) })
s3: com.eed3si9n.tetrix.GameState = GameState(List(Block((0,0),TKind), Block((1,0),TKind), Block((2,0),TKind), Block((3,0),TKind), Block((7,0),TKind), Block((8,0),TKind), Block((9,0),TKind), Block((4,17),TKind), Block((5,17),TKind), Block((6,17),TKind), Block((5,18),TKind)),(10,20),Piece((5.0,17.0),TKind,List((-1.0,0.0), (0.0,0.0), (1.0,0.0), (0.0,1.0))))

scala> val s = Function.chain(Nil padTo (17, tick))(s3)
s: com.eed3si9n.tetrix.GameState = GameState(List(Block((0,0),TKind), Block((1,0),TKind), Block((2,0),TKind), Block((3,0),TKind), Block((7,0),TKind), Block((8,0),TKind), Block((9,0),TKind), Block((4,0),TKind), Block((5,0),TKind), Block((6,0),TKind), Block((5,1),TKind)),(10,20),Piece((5.0,0.0),TKind,List((-1.0,0.0), (0.0,0.0), (1.0,0.0), (0.0,1.0))))
``````