finish ch3/some exercises

ch3/variables/src/main.rs

@@ -138,6 +138,142 @@ fn main() {
     //------------------------------------------------------------------------
     let num = plus_one(five());
     println!("The value of num is: {num}");
+
+    //------------------------------------------------------------------------
+    // ch3.4 About commments
+
+    /*
+        This is a multiline comment pog
+        Documentation comments are covered in chapter 14.
+    */
+
+    //------------------------------------------------------------------------
+    // ch3.5 control flow
+
+    // let number = 3;
+    let number = 7;
+
+    // The condition must evaluate to a bool.
+    if number < 5 {
+        println!("condition true");
+    } else {
+        println!("condition false");
+    }
+
+    if number != 0 {
+        println!("Number is not 0");
+    }
+
+    let new_num = 6;
+
+    if new_num % 4 == 0 {
+        println!("new_num is divisible by 4");
+    } else if new_num % 3 == 0 {
+        println!("new_num divisible by 3");
+    } else if new_num % 2 == 0 {
+        println!("new_num divisible by 2");
+    } else {
+        println!("new_num not divisible by 4, 3, or 2");
+    }
+
+    //------------------------------------------------------------------------
+
+    let condition = true;
+    let cond_num = if condition { 5 } else { 6 }; // can't mismatch types this way.
+    println!("The value of cond_num is: {cond_num}");
+
+    //------------------------------------------------------------------------
+    let val = if condition { 1 } else { 2 };
+    let new_val;
+    if condition {
+        // referencing new_val from above within this if statement scope.
+        // Still a bit iffy on how the memory management works.
+        new_val = 1;
+    } else {
+        new_val = 2
+    };
+    println!("new_val = {new_val}");
+
+    //------------------------------------------------------------------------
+    // Looping syntax
+
+    let mut counter = 0;
+    // can grab a value from a loop statement
+    let result = loop {
+        println!("again!");
+        if counter == 10 {
+            break counter * 2;
+        }
+        counter += 1;
+    };
+    println!("The result is: {result}");
+
+    //------------------------------------------------------------------------
+    // loop labels :eyes:
+
+    let mut count = 0;
+    'counting_up: loop {
+        // clojure where :eyes:
+        println!("count = {count}");
+        let mut remaining = 10;
+
+        loop {
+            println!("remaining = {remaining}");
+            if remaining == 9 {
+                break;
+            }
+            if count == 2 {
+                break 'counting_up;
+            }
+            remaining -= 1;
+        }
+        count += 1;
+    }
+    println!("End count = {count}");
+
+    //------------------------------------------------------------------------
+    // While loop
+
+    let mut while_num = 3;
+
+    while while_num != 0 {
+        println!("while_num: {while_num}");
+        while_num -= 1;
+    }
+    println!("LIFTOFFFFFFF (while_num reached 0)");
+
+    //------------------------------------------------------------------------
+    // For loop
+
+    let for_arr = [10, 20, 30, 40, 50];
+    let mut index = 0;
+
+    // The old, unpog way of doing this
+    while index < 5 {
+        println!("while value is: {}", for_arr[index]);
+        index += 1;
+    }
+
+    // The new, pog way of doing this
+    for element in for_arr {
+        println!("for value is: {element}");
+    }
+
+    // for loop recreation of liftoff above
+    for pog_num in (1..4).rev() {
+        println!("{pog_num}");
+    }
+    println!("for LIFTOFFFFFF!");
+
+    //------------------------------------------------------------------------
+    // Summary questions at the end of the ch3.5
+
+    let ftc = fahrenheit_to_celsius(32.1);
+    println!("fahrenheit to celsius of 32.0 degress F: {ftc}");
+    let ctf = celsius_to_fahrenheit(5.0);
+    println!("celsius_to_fahrenheitof 5.0 degrees C: {ctf}");
+    let fib_num = fibonacci(5);
+    println!("fibonacci of fib_num: {fib_num}");
 }
 
 // Statements: Instructions that perform some action and don't return anything
@@ -166,3 +302,24 @@ fn five() -> i32 {
 fn plus_one(x: i32) -> i32 {
     x + 1
 }
+
+// ch3.5 exercise
+fn fahrenheit_to_celsius(temp: f64) -> f64 {
+    (temp - 32.0) * (5.0 / 9.0)
+}
+
+// ch3.5 exercise
+fn celsius_to_fahrenheit(temp: f64) -> f64 {
+    (9.0 / 5.0) * temp + 32.0
+}
+
+fn fibonacci(num: usize) -> usize {
+    if num == 0 {
+        return 0;
+    } else if num == 1 {
+        return 1;
+    }
+    fibonacci(num - 1) + fibonacci(num - 2)
+}
+
+// I'm not programming the christmas carol song