refactor exercise e to use integers instead of strings, stop using ar…

…gs, stop using functions

exercise/e_control_flow/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "d_control_flow_strings"
+name = "e_control_flow"
 version = "0.1.0"
 edition = "2021"
 

exercise/e_control_flow/src/main.rs

@@ -1,57 +1,67 @@
 // Silence some warnings so they don't distract from the exercise.
-#![allow(dead_code, unused_mut, unused_variables)]
+#![allow(unused_mut, unused_variables)]
 
 fn main() {
-    // This collects any command-line arguments into a vector of Strings.
-    // For example:
+    // 1. Use an unconditional `loop` to count how many times we can double `bunnies` until there
+    // are over 500 bunnies. (Hint: The answer is 8 times)
     //
-    //     cargo run apple banana
-    //
-    // ...produces an 'args' variable with the equivalent of:
-    //
-    //     vec!["apple".to_string(), "banana".to_string()]
-    let args: Vec<String> = std::env::args().skip(1).collect();
-
-    // This consumes the `args` vector to iterate through each String
-    for arg in args {
-        // 1a. Your task: handle the command-line arguments!
-        //
-        // - If arg is "sum", then call the sum() function
-        // - If arg is "double", then call the double() function
-        // - If arg is anything else, then call the count() function, passing "arg" to it.
-
-        // 1b. Now try passing "sum", "double" and "bananas" to the program by adding your argument
-        // after "cargo run".  For example "cargo run sum"
-    }
-}
-
-fn sum() {
-    let mut sum = 0;
-    // 2. Use a "for loop" to iterate through integers from 7 to 23 *inclusive* using a range
-    // and add them all together (increment the `sum` variable).  Hint: You should get 255
-    // Run it with `cargo run sum`
-
-    println!("The sum is {}", sum);
-}
+    // Inside the loop:
+    // - Add 1 to `count`
+    // - Multiply `bunnies` by 2
+    // - If `bunnies` is larger than 500, break out of the loop.
 
-fn double() {
     let mut count = 0;
-    let mut x = 1;
-    // 3. Use a "while loop" to count how many times you can double the value of `x` (multiply `x`
-    // by 2) until `x` is larger than 500.  Increment `count` each time through the loop. Run it
-    // with `cargo run double`  Hint: The answer is 9 times.
+    let mut bunnies = 2;
+
+    // (write your `loop` here)
 
     println!(
-        "You can double x {} times until x is larger than 500",
+        "Bunnies doubled {} times before there were more than 500",
         count
     );
-}
 
-fn count(arg: String) {
-    // Challenge: Use an unconditional loop (`loop`) to print `arg` 8 times, and then break.
-    // You will need to count your loops, somehow.  Run it with `cargo run bananas`
+    // 2. Use a `for` loop to iterate through integers from 7 to 23 *inclusive* using a range
+    // and add them all together (add each value to the `sum` variable).  Hint: You should get 255
+
+    let mut sum = 0;
+
+    // (write the `for` loop here)
+
+    println!("The sum is {}", sum);
+
+    // 3. Use a `while` loop to create a vector containing the first 12 multiples of 5.
+    //
+    // The loop should continue until `fives.len()` returns 12.
+    //
+    // Each time through the loop, call `fives.push( ... )` to push `current_five` onto the vector,
+    // and then add 5 to `current_five`.
+
+    let mut fives: Vec<i32> = vec![];
+    let mut current_five = 5;
+
+    // (write the `while` loop here)
+
+    println!("Here are the first 12 multiples of 5: {:?}", fives);
+
+    // 4. Use `if`, `else if` and `else` inside the `for` loop below to do the following:
     //
-    // print!("{} ", arg); // Execute this line 8 times, and then break. `print!` doesn't add a newline.
+    // - If the number is 0, then add 7 to `total`
+    // - If the number is 1 or 2 then add 30 to `total`
+    // - If the number is anything else, subtract 5 from `total`
+    //
+    // Hint: The total should be 52
 
-    println!(); // This will output just a newline at the end for cleanliness.
+    let mut total = 0;
+    let numbers = vec![0, 1, 2, 3, 4, 5];
+    for number in numbers {
+        // (write your `if/else` expression here)
+    }
+
+    println!("The total is {}", total);
+
+    // Challenge: Change the implementation of your answers to #1-#3 as follows:
+    //
+    // - Change #1 to use `while`
+    // - Change #2 to use `loop`
+    // - Change #3 to use `for` and a range (multiply the range value by 5 inside your loop before
 }