ch5 start

ch5/defining_instantiating_structs/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "defining_instantiating_structs"
+version = "0.1.0"

ch5/defining_instantiating_structs/Cargo.toml

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+[package]
+name = "defining_instantiating_structs"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

ch5/defining_instantiating_structs/src/main.rs

@@ -0,0 +1,53 @@
+struct User {
+    active: bool,
+    username: String, // using &str wont compile
+    email: String,    // needs a lifetime which & doesn't do
+    sign_in_count: u64,
+}
+
+// Just like haskell :)
+#[derive(Debug)]
+struct Color(i32, i32, i32);
+#[derive(Debug)]
+struct Point(i32, i32, i32);
+
+struct AlwaysEqual;
+
+fn main() {
+    let mut user1 = User {
+        email: String::from("email@mail.org"),
+        username: String::from("username"),
+        active: true,
+        sign_in_count: 1,
+    };
+    user1.email = String::from("new_email@mail.org");
+
+    // update syntax
+    // borrows from user1, deallocating only the copied variables in the process.
+    // The variables not borrowed are left alone. Rust is cool
+    let user2 = User {
+        // active: user1.active,
+        // username: user1.username,
+        email: String::from("other_email@mail.org"),
+        // sign_in_count: user1.sign_in_count,
+        ..user1 // can do this for copying fields over on the shorthand
+    };
+
+    let black = Color(0, 0, 0);
+    let origin = Point(0, 0, 0);
+
+    println!("black: {:?}", black);
+    println!("origin: {:?}", origin);
+
+    // unit-like structs without any fields
+    let subject = AlwaysEqual;
+}
+
+fn build_user(email: String, username: String) -> User {
+    User {
+        active: true,
+        username, // use a shorthand because this errors if not using a shorthand?
+        email,    // That might have just been linting
+        sign_in_count: 1,
+    }
+}

ch5/example_structs/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "example_structs"
+version = "0.1.0"

ch5/example_structs/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "example_structs"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

ch5/example_structs/src/main.rs

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+#[derive(Debug)]
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+fn main() {
+    let rect1 = Rectangle {
+        width: 30,
+        height: 50,
+    };
+
+    // prints to stdout
+    println!("Area of rect is: {:?} units", area(&rect1));
+    println!("rect1 is: {rect1:#?}");
+
+    // prints to stderr
+    dbg!(&rect1);
+}
+
+fn area(rect: &Rectangle) -> u32 {
+    rect.width * rect.height
+}

ch5/method_syntax/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "method_syntax"
+version = "0.1.0"

ch5/method_syntax/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "method_syntax"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

ch5/method_syntax/src/main.rs

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+#[derive(Debug)]
+struct Rectangle {
+    width: u32,
+    height: u32,
+}
+
+// it is rare to see just "self" alone.
+// Typically always see "&self"
+// This is also very similar to Haskell
+impl Rectangle {
+    // urhmm actkually these are *methods* and not *functions*
+    fn area(&self) -> u32 {
+        self.width * self.height
+    }
+
+    fn width(&self) -> bool {
+        self.width > 0
+    }
+}
+
+fn main() {
+    let rect1 = Rectangle {
+        width: 30,
+        height: 50,
+    };
+
+    println!(
+        "The area of the rectangle is {} square pixels.",
+        rect1.area()
+    );
+
+    if rect1.width() {
+        println!("rect has a nonzero width; it is: {}", rect1.width);
+    }
+
+    // stopped here:
+    // https://rust-book.cs.brown.edu/ch05-03-method-syntax.html#methods-and-ownership
+}