wording

[rust-101.git] / workspace / src / part02.rs

diff --git a/workspace/src/part02.rs b/workspace/src/part02.rs
index 8d1c8b69c3fce7bea45c73efd06983e3c419a92f..357c5a04dd7164f3a20fba737cc5b2b7d1373671 100644 (file)
--- a/workspace/src/part02.rs
+++ b/workspace/src/part02.rs
@@ -1 +1,83 @@
- 
+// Rust-101, Part 02: Generic types, Traits
+// ========================================
+
+
+// ## Generic datatypes
+
+pub enum SomethingOrNothing<T>  {
+    Something(T),
+    Nothing,
+}
+// Instead of writing out all the variants, we can also just import them all at once.
+pub use self::SomethingOrNothing::*;
+type NumberOrNothing = SomethingOrNothing<i32>;
+
+// ## Generic `impl`, Static functions
+// Inside an `impl`, `Self` refers to the type we are implementing things for. Here, it is
+// an alias for `SomethingOrNothing<T>`.
+impl<T> SomethingOrNothing<T> {
+    fn new(o: Option<T>) -> Self {
+        unimplemented!()
+    }
+
+    fn to_option(self) -> Option<T> {
+        unimplemented!()
+    }
+}
+// You can call static functions, and in particular constructors, as demonstrated in `call_constructor`.
+fn call_constructor(x: i32) -> SomethingOrNothing<i32> {
+    SomethingOrNothing::new(Some(x))
+}
+
+// ## Traits
+
+pub trait Minimum : Copy {
+    fn min(self, b: Self) -> Self;
+}
+
+pub fn vec_min<T: Minimum>(v: Vec<T>) -> SomethingOrNothing<T> {
+    let mut min = Nothing;
+    for e in v {
+        min = Something(match min {
+            Nothing => e,
+            // Here, we can now call the `min` function of the trait.
+            Something(n) => {
+                unimplemented!()
+            }
+        });
+    }
+    min
+}
+
+// ## Trait implementations
+// To make `vec_min` usable with a `Vec<i32>`, we implement the `Minimum` trait for `i32`.
+impl Minimum for i32 {
+    fn min(self, b: Self) -> Self {
+        unimplemented!()
+    }
+}
+
+// We again provide a `print` function.
+impl NumberOrNothing {
+    pub fn print(self) {
+        match self {
+            Nothing => println!("The number is: <nothing>"),
+            Something(n) => println!("The number is: {}", n),
+        };
+    }
+}
+
+// Now we are ready to run our new code. Remember to change `main.rs` appropriately.
+fn read_vec() -> Vec<i32> {
+    vec![18,5,7,3,9,27]
+}
+pub fn main() {
+    let vec = read_vec();
+    let min = vec_min(vec);
+    min.print();
+}
+
+
+// **Exercise 02.1**: Change your program such that it computes the minimum of a `Vec<f32>` (where `f32` is the type
+// of 32-bit floating-point numbers). You should not change `vec_min` in any way, obviously!
+