8 files changed, 295 insertions, 0 deletions
diff --git a/meap/meap-code/ch4/ch4-check-sats-1.rs b/meap/meap-code/ch4/ch4-check-sats-1.rs
new file mode 100644
index 0000000..254c866
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-check-sats-1.rs
@@ -0,0 +1,27 @@
+#![allow(unused_variables)]
+
+#[derive(Debug)]
+enum StatusMessage {
+  Ok,
+}
+
+fn check_status(sat_id: u64) -> StatusMessage {
+  StatusMessage::Ok
+}
+
+fn main () {
+  let sat_a = 0;
+  let sat_b = 1;
+  let sat_c = 2;
+
+  let a_status = check_status(sat_a);
+  let b_status = check_status(sat_b);
+  let c_status = check_status(sat_c);
+  println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+
+  // "waiting" ...
+  let a_status = check_status(sat_a);
+  let b_status = check_status(sat_b);
+  let c_status = check_status(sat_c);
+  println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+}
diff --git a/meap/meap-code/ch4/ch4-check-sats-3.rs b/meap/meap-code/ch4/ch4-check-sats-3.rs
new file mode 100644
index 0000000..58a65cd
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-check-sats-3.rs
@@ -0,0 +1,33 @@
+#![allow(unused_variables)]
+
+#[derive(Debug)]
+struct CubeSat {
+  id: u64,
+}
+
+#[derive(Debug)]
+enum StatusMessage {
+  Ok,
+}
+
+fn check_status(sat_id: CubeSat) -> CubeSat {
+  println!("{:?}: {:?}", sat_id, StatusMessage::Ok);
+  sat_id
+}
+
+fn main () {
+  let sat_a = CubeSat { id: 0 };
+  let sat_b = CubeSat { id: 1 };
+  let sat_c = CubeSat { id: 2 };
+
+  let sat_a = check_status(sat_a);
+  let sat_b = check_status(sat_b);
+  let sat_c = check_status(sat_c);
+  // println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+
+  // "waiting" ...
+  let sat_a = check_status(sat_a);
+  let sat_b = check_status(sat_b);
+  let sat_c = check_status(sat_c);
+  //println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+}
diff --git a/meap/meap-code/ch4/ch4-check-sats-clone-and-copy-traits.rs b/meap/meap-code/ch4/ch4-check-sats-clone-and-copy-traits.rs
new file mode 100644
index 0000000..df17ed5
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-check-sats-clone-and-copy-traits.rs
@@ -0,0 +1,24 @@
+#[derive(Debug,Copy)]
+struct CubeSat {
+  id: u64,
+}
+
+#[derive(Debug,Copy)]
+enum StatusMessage {
+  Ok,
+}
+
+
+fn check_status(sat_id: CubeSat) -> StatusMessage {
+  StatusMessage::Ok
+}
+
+fn main () {
+  let sat_a = CubeSat { id: 0 };
+
+  let a_status = check_status(sat_a.clone());
+  println!("a: {:?}", a_status.clone();
+
+  let a_status = check_status(sat_a);
+  println!("a: {:?}", a_status);
+}
diff --git a/meap/meap-code/ch4/ch4-check-sats-with-copy-trait.rs b/meap/meap-code/ch4/ch4-check-sats-with-copy-trait.rs
new file mode 100644
index 0000000..4126e05
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-check-sats-with-copy-trait.rs
@@ -0,0 +1,46 @@
+#[derive(Debug)]
+struct CubeSat {
+  id: u64,
+}
+
+#[derive(Debug)]
+enum StatusMessage {
+  Ok,
+}
+
+impl Copy for CubeSat { }
+
+impl Copy for StatusMessage { }
+
+impl Clone for CubeSat { // <1>
+  fn clone(&self) -> Self {
+    CubeSat { id: self.id } //<2>
+  }
+}
+
+impl Clone for StatusMessage {
+  fn clone(&self) -> Self {
+    *self // <3>
+  }
+}
+
+fn check_status(sat_id: CubeSat) -> StatusMessage {
+  StatusMessage::Ok
+}
+
+fn main () {
+  let sat_a = CubeSat { id: 0 };
+  let sat_b = CubeSat { id: 1 };
+  let sat_c = CubeSat { id: 2 };
+
+  let a_status = check_status(sat_a);
+  let b_status = check_status(sat_b);
+  let c_status = check_status(sat_c);
+  println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+
+  // "waiting" ...
+  let a_status = check_status(sat_a);
+  let b_status = check_status(sat_b);
+  let c_status = check_status(sat_c);
+  println!("a: {:?}, b: {:?}, c: {:?}", a_status, b_status, c_status);
+}
diff --git a/meap/meap-code/ch4/ch4-rc-groundstation.rs b/meap/meap-code/ch4/ch4-rc-groundstation.rs
new file mode 100644
index 0000000..c51f865
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-rc-groundstation.rs
@@ -0,0 +1,10 @@
+use std::rc::Rc;
+
+#[derive(Debug)]
+struct GroundStation {}
+
+fn main() {
+  let base: Rc<GroundStation> = Rc::new(GroundStation {});
+  
+  println!("{:?}", base);
+}
+\ No newline at end of file
diff --git a/meap/meap-code/ch4/ch4-rc-refcell-groundstation.rs b/meap/meap-code/ch4/ch4-rc-refcell-groundstation.rs
new file mode 100644
index 0000000..d0e27ee
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-rc-refcell-groundstation.rs
@@ -0,0 +1,31 @@
+use std::rc::Rc;
+use std::cell::RefCell;
+
+#[derive(Debug)]
+struct GroundStation {
+  radio_freq: f64 // Mhz
+}
+
+fn main() {
+  let base: Rc<RefCell<GroundStation>> = Rc::new(RefCell::new(
+    GroundStation {
+      radio_freq: 87.65
+    }
+  ));
+
+  println!("base: {:?}", base);
+
+  { // introduce a new scope
+    let mut base_2 = base.borrow_mut();
+    base_2.radio_freq -= 12.34;
+    println!("base_2: {:?}", base_2);
+  }
+
+  println!("base: {:?}", base);
+
+  let mut base_3 = base.borrow_mut();
+  base_3.radio_freq += 43.21;
+
+  println!("base: {:?}", base);
+  println!("base_3: {:?}", base_3);
+}
diff --git a/meap/meap-code/ch4/ch4-sat-mailbox.rs b/meap/meap-code/ch4/ch4-sat-mailbox.rs
new file mode 100644
index 0000000..81f292d
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-sat-mailbox.rs
@@ -0,0 +1,42 @@
+
+#[derive(Debug)]
+struct CubeSat {
+  id: u64,
+  mailbox: Mailbox,
+}
+
+#[derive(Debug)]
+struct Mailbox {
+  messages: Vec<Message>,
+}
+
+type Message = String;
+
+struct GroundStation;
+
+impl GroundStation {
+    fn send(&self, to: &mut CubeSat, msg: Message) {
+        to.mailbox.messages.push(msg);
+    }
+}
+
+impl CubeSat {
+    fn recv(&mut self) -> Option<Message> {
+        self.mailbox.messages.pop()
+    }
+}
+
+fn main() {
+    let base = GroundStation {};
+    let mut sat_a = CubeSat { id: 0, mailbox: Mailbox { messages: vec![] } };
+
+    println!("t0: {:?}", sat_a);
+    base.send(&mut sat_a, Message::from("hello there!")); // <1>
+
+    println!("t1: {:?}", sat_a);
+
+    let msg = sat_a.recv();
+    println!("t2: {:?}", sat_a);
+
+    println!("msg: {:?}", msg);
+}
diff --git a/meap/meap-code/ch4/ch4-short-lived-strategy.rs b/meap/meap-code/ch4/ch4-short-lived-strategy.rs
new file mode 100644
index 0000000..1082469
--- /dev/null
+++ b/meap/meap-code/ch4/ch4-short-lived-strategy.rs
@@ -0,0 +1,82 @@
+#![allow(unused_variables)]
+
+#[derive(Debug)]
+struct CubeSat {
+  id: u64,
+}
+
+#[derive(Debug)]
+struct Mailbox {
+  messages: Vec<Message>,
+}
+
+#[derive(Debug)]
+struct Message {
+    to: u64,
+    content: String,
+}
+
+struct GroundStation {}
+
+impl Mailbox {
+    fn post(&mut self, msg: Message) {
+        self.messages.push(msg);
+    }
+
+    fn deliver(&mut self, recipient: &CubeSat) -> Option<Message> {
+        for i in 0..self.messages.len() {
+            if self.messages[i].to == recipient.id {
+                let msg = self.messages.remove(i);
+                return Some(msg);
+            }
+        }
+
+        None
+    }
+}
+
+impl GroundStation {
+    fn connect(&self, sat_id: u64) -> CubeSat {
+        CubeSat {
+            id: sat_id, 
+        }
+    }
+
+    fn send(&self, mailbox: &mut Mailbox, msg: Message) {
+        mailbox.post(msg);
+    }
+}
+
+impl CubeSat {
+    fn recv(&self, mailbox: &mut Mailbox) -> Option<Message> {
+        mailbox.deliver(&self)
+    }
+}
+
+fn fetch_sat_ids() -> Vec<u64> {
+  vec![1,2,3]
+}
+
+
+fn main() {
+  let mut mail = Mailbox { messages: vec![] };
+
+  let base = GroundStation {};
+
+  let sat_ids = fetch_sat_ids();
+
+  for sat_id in sat_ids {
+    let sat = base.connect(sat_id);
+    let msg = Message { to: sat_id, content: String::from("hello") };
+    base.send(&mut mail, msg);
+  }
+
+  let sat_ids = fetch_sat_ids();
+
+  for sat_id in sat_ids {
+    let sat = base.connect(sat_id);
+    
+    let msg = sat.recv(&mut mail);
+    println!("{:?}: {:?}", sat, msg);
+  }
+}
+\ No newline at end of file