-// ***Remember to enable/add this part in `main.rs`!***
-
-// Rust-101, Part 00: Algebraic datatypes
-// ======================================
-
-// As our first piece of Rust code, we want to write a function that computes the
-// minimum of a list.
-
-
-// An `enum` for "a number or nothing" could look as follows:
-enum NumberOrNothing {
- Number(i32),
- Nothing
-}
-
-// Observe how in Rust, the return type comes *after* the arguments.
-fn vec_min(vec: Vec<i32>) -> NumberOrNothing {
- let mut min = NumberOrNothing::Nothing;
-
- // Now we want to *iterate* over the list. Rust has some nice syntax for
- // iterators:
- for el in vec {
- // So `el` is al element of the list. We need to update `min` accordingly, but how do we get the current
- // number in there? This is what pattern matching can do:
- match min {
- // In this case (*arm*) of the `match`, `min` is currently nothing, so let's just make it the number `el`.
- NumberOrNothing::Nothing => {
- unimplemented!()
- },
- // In this arm, `min` is currently the number `n`, so let's compute the new minimum and store it. We will write
- // the function `min_i32` just after we completed this one.
- NumberOrNothing::Number(n) => {
- unimplemented!()
- }
- }
- }
- // Finally, we return the result of the computation.
- return min;
-}
-
-// Now that we reduced the problem to computing the minimum of two integers, let's do that.
-fn min_i32(a: i32, b: i32) -> i32 {
- if a < b {
- unimplemented!()
- } else {
- unimplemented!()
- }
-}
-
-// Phew. We wrote our first Rust function! But all this `NumberOrNothing::` is getting kind of
-// ugly. Can't we do that nicer?
-
-// Indeed, we can: The following line tells Rust to take
-// the constructors of `NumberOrNothing` into the local namespace.
-// Try moving that above the function, and removing all the occurrences `NumberOrNothing::`.
-use self::NumberOrNothing::{Number,Nothing};
-
-// To call this function, we now just need a list. Of course, ultimately we want to ask the user for
-// a list of numbers, but for now, let's just hard-code something.
-
-// `vec!` is a *macro* (as you can tell from the `!`) that constructs a constant `Vec<_>` with the given
-// elements.
-fn read_vec() -> Vec<i32> {
- vec![18,5,7,1,9,27]
-}
-
-// Finally, let's call our functions and run the code!
-// But, wait, we would like to actually see something, so we need to print the result.
-// Of course Rust can print numbers, but after calling `vec_min`, we have a `NumberOrNothing`.
-// So let's write a small helper function that prints such values.
-
-fn print_number_or_nothing(n: NumberOrNothing) {
- match n {
- Nothing => println!("The number is: <nothing>"),
- Number(n) => println!("The number is: {}", n),
- };
-}
-
-// Putting it all together:
-pub fn main() {
- let vec = read_vec();
- let min = vec_min(vec);
- print_number_or_nothing(min);
-}
-
-// Now try `cargo run` on the console to run above code.
-
-
-// [index](main.html) | previous | [next](part01.html)