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remove unnecessary mut borrow and write access in chap 2 #194

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remove unnecessary mut borrow and write access in chap 2 #194

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3496aad
remove unnecessary mut borrow and write access
xysun Jul 31, 2022
d757808
update book text
xysun Jul 31, 2022
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6 changes: 3 additions & 3 deletions book/src/chapter_2.md
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Original file line number Diff line number Diff line change
Expand Up @@ -547,9 +547,9 @@ Now we implement a new function, `try_move_player`:
```rust
fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
let mut positions = ecs.write_storage::<Position>();
let mut players = ecs.write_storage::<Player>();
let players = ecs.read_storage::<Player>();

for (_player, pos) in (&mut players, &mut positions).join() {
for (_player, pos) in (&players, &mut positions).join() {
pos.x = min(79 , max(0, pos.x + delta_x));
pos.y = min(49, max(0, pos.y + delta_y));
}
Expand All @@ -561,7 +561,7 @@ Drawing on our previous experience, we can see that this gains write access to `
We'll add a second function to read the keyboard information provided by RLTK:

```rust
fn player_input(gs: &mut State, ctx: &mut Rltk) {
fn player_input(gs: &mut State, ctx: &Rltk) {
// Player movement
match ctx.key {
None => {} // Nothing happened
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6 changes: 3 additions & 3 deletions chapter-02-helloecs/src/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,15 +28,15 @@ struct State {

fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
let mut positions = ecs.write_storage::<Position>();
let mut players = ecs.write_storage::<Player>();
let players = ecs.read_storage::<Player>();

for (_player, pos) in (&mut players, &mut positions).join() {
for (_player, pos) in (&players, &mut positions).join() {
pos.x = min(79 , max(0, pos.x + delta_x));
pos.y = min(49, max(0, pos.y + delta_y));
}
}

fn player_input(gs: &mut State, ctx: &mut Rltk) {
fn player_input(gs: &mut State, ctx: &Rltk) {
// Player movement
match ctx.key {
None => {} // Nothing happened
Expand Down