Add thread example

Author: CoderSales

documentation2/B09-Thread.md

@@ -0,0 +1,65 @@
+# [Thread](https://www.programiz.com/rust/thread)
+
+A thread is the smallest executable unit of a process.
+
+Threads allow us to split the computation in our program into multiple threads. Running multiple tasks at the same time can improve performance of the code. However, it can add complexity.
+
+____
+
+## Creating a New Thread in Rust
+
+In Rust, we can create a native operating system thread using the `thread::spawn()` function from the `std` module. The spawn method takes a closure as an argument.
+
+Here is the syntax of `thread::spawn()`,
+
+```rust
+thread::spawn(|| {
+    // code to execute in the thread 
+})
+```
+
+Now, let's see an example.
+
+```rust
+use std::thread;
+use std::time::Duration;
+
+fn main() {
+    // create a thread
+    thread::spawn(|| {
+        // everything in here runs in a separate thread
+        for i in 0..10 {
+            println!("{} from the spawned thread!", i);
+            thread::sleep(Duration::from_millis(2));
+        }
+    });
+
+    // main thread
+    for i in 0..5 {
+        println!("{} from the main thread!", i);
+        thread::sleep(Duration::from_millis(1));
+    }
+}
+```
+
+```bash
+cargo build
+```
+
+```bash
+cargo run
+```
+
+### Output
+
+```bash
+0 from the main thread!
+0 from the spawned thread!
+1 from the main thread!
+1 from the spawned thread!
+2 from the main thread!
+3 from the main thread!
+2 from the spawned thread!
+4 from the main thread!
+3 from the spawned thread!
+```

programiz/attempt-02/hello_world/src/main.rs

@@ -1,14 +1,19 @@
-// A macro which uses repetitions
-macro_rules! repeat_print {
-    // match rule which matches multiple expressions in an argument
-    ($($x:expr),*) => {
-        $(
-            println!("{}", $x);
-        )*
-    };
-}
+use std::thread;
+use std::time::Duration;
 
 fn main() {
-    // Call the macro with multiple arguments
-    repeat_print!(1, 2, 3);
+    // create a thread
+    thread::spawn(|| {
+        // everything in here runs in a separate thread
+        for i in 0..10 {
+            println!("{} from the spawned thread!", i);
+            thread::sleep(Duration::from_millis(2));
+        }
+    });
+
+    // main thread
+    for i in 0..5 {
+        println!("{} from the main thread!", i);
+        thread::sleep(Duration::from_millis(1));
+    }
 }