Merge amethyst#899

899: add imports to pong-tutorial-03.md and make pong.rs things pub r=jojolepro a=jackmott

This addresses amethyst#898 , I added the necessary includes to paddle.rs in the code examples. As well, on page 2, I made the elements that need to be public, pub, which I think will avoid confusion vs making them private then having to notice the offhand comment on page 3 to change them to public.

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Co-authored-by: jack mott <[email protected]>

book/src/pong-tutorial/pong-tutorial-02.md

@@ -84,11 +84,12 @@ that will determine what is rendered on screen. It behaves just like a
 real life camera: it records a specific part of the world and can be
 moved around at will.
 
-First, let's define some constants:
+First, let's define some constants. We will make them public for use in other
+modules later:
 
 ```rust,no_run,noplaypen
-const ARENA_HEIGHT: f32 = 100.0;
-const ARENA_WIDTH: f32 = 100.0;
+pub const ARENA_HEIGHT: f32 = 100.0;
+pub const ARENA_WIDTH: f32 = 100.0;
 ```
 
 These constants will determine the size of our arena.
@@ -153,16 +154,17 @@ much better from then on, we promise!
 
 ## Our first Component
 
-In `pong.rs` let's create our first `Component`, a definition of a paddle.
+In `pong.rs` let's create our first `Component`, a definition of a paddle. We
+will make `Side` and `Paddle` public for use in other modules later.
 
 ```rust,no_run,noplaypen
 #[derive(PartialEq, Eq)]
-enum Side {
+pub enum Side {
     Left,
     Right,
 }
 
-struct Paddle {
+pub struct Paddle {
     pub side: Side,
     pub width: f32,
     pub height: f32,

book/src/pong-tutorial/pong-tutorial-03.md

@@ -110,7 +110,6 @@ use amethyst::input::InputHandler;
 # impl amethyst::ecs::Component for Paddle {
 #   type Storage = amethyst::ecs::VecStorage<Paddle>;    
 # }
-
 pub struct PaddleSystem;
 
 impl<'s> System<'s> for PaddleSystem {
@@ -139,8 +138,11 @@ impl<'s> System<'s> for PaddleSystem {
   }
 }
 ```
+Note: You will also need to add a `use` statement to bring in `Paddle` and `Side` from pong.rs:
 
-Note: We had to make our Paddle and Side public in `pong.rs`
+```rust,ignore
+use pong::{Paddle, Side, ARENA_HEIGHT, PADDLE_HEIGHT};
+```
 
 Now lets add this system to our `GameDataBuilder` in `main.rs`: