X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/c25f3400060ea1a02f8fa9de69c39fd7b020e8a5..3a94cd0261c4cd5c348eb1c1359106b76f01e518:/src/part02.rs diff --git a/src/part02.rs b/src/part02.rs index bd8abf0..44a20d4 100644 --- a/src/part02.rs +++ b/src/part02.rs @@ -17,13 +17,13 @@ pub enum SomethingOrNothing { } // Instead of writing out all the variants, we can also just import them all at once. pub use self::SomethingOrNothing::*; -//@ What this does is to define an entire family of types: We can now write +//@ What this does is define an entire family of types: We can now write //@ `SomethingOrNothing` to get back our `NumberOrNothing`. type NumberOrNothing = SomethingOrNothing; //@ However, we can also write `SomethingOrNothing` or even `SomethingOrNothing>`. -//@ In fact, such a type is so useful that it is already present in the standard library: It's called an -//@ *option type*, written `Option`. Go check out its [documentation](http://doc.rust-lang.org/stable/std/option/index.html)! -//@ (And don't worry, there's indeed lots of material mentioned there that we did not cover yet.) +//@ In fact, a type like `SomethingOrNothing` is so useful that it is already present in the standard library: It's called an +//@ *option type*, written `Option`. Go check out its [documentation](https://doc.rust-lang.org/stable/std/option/index.html)! +//@ (And don't worry, there's indeed lots of material mentioned there that we have not covered yet.) // ## Generic `impl`, Static functions //@ The types are so similar, that we can provide a generic function to construct a `SomethingOrNothing` @@ -55,7 +55,7 @@ fn call_constructor(x: i32) -> SomethingOrNothing { } // ## Traits -//@ Now that we have a generic `SomethingOrNothing`, wouldn't it be nice to also gave a generic +//@ Now that we have a generic `SomethingOrNothing`, wouldn't it be nice to also have a generic //@ `vec_min`? Of course, we can't take the minimum of a vector of *any* type. It has to be a type //@ supporting a `min` operation. Rust calls such properties that we may demand of types *traits*. @@ -63,10 +63,10 @@ fn call_constructor(x: i32) -> SomethingOrNothing { //@ For now, just ignore the `Copy`, we will come back to this point later. //@ A `trait` is a lot like interfaces in Java: You define a bunch of functions //@ you want to have implemented, and their argument and return types.
-//@ The function `min` takes to arguments of the same type, but I made the +//@ The function `min` takes two arguments of the same type, but I made the //@ first argument the special `self` argument. I could, alternatively, have //@ made `min` a static function as follows: `fn min(a: Self, b: Self) -> Self`. -//@ However, in Rust one typically prefers methods over static function wherever possible. +//@ However, in Rust one typically prefers methods over static functions wherever possible. pub trait Minimum : Copy { fn min(self, b: Self) -> Self; } @@ -98,7 +98,7 @@ pub fn vec_min(v: Vec) -> SomethingOrNothing { //@ Before going on, take a moment to ponder the flexibility of Rust's take on abstraction: //@ We just defined our own, custom trait (interface), and then implemented that trait //@ *for an existing type*. With the hierarchical approach of, e.g., C++ or Java, -//@ that's not possible: We cannot make an existing type suddenly also inherit from our abstract base class. +//@ that's not possible: We cannot make an existing type also inherit from our abstract base class after the fact. //@ //@ In case you are worried about performance, note that Rust performs *monomorphisation* //@ of generic functions: When you call `vec_min` with `T` being `i32`, Rust essentially goes @@ -141,9 +141,9 @@ pub fn main() { min.print(); } -//@ If this printed `3`, then you generic `vec_min` is working! So get ready for the next part. +//@ If this printed `3`, then your generic `vec_min` is working! So get ready for the next part. // **Exercise 02.1**: Change your program such that it computes the minimum of a `Vec` (where `f32` is the type // of 32-bit floating-point numbers). You should not change `vec_min` in any way, obviously! -//@ [index](main.html) | [previous](part01.html) | [next](part03.html) +//@ [index](main.html) | [previous](part01.html) | [raw source](https://www.ralfj.de/git/rust-101.git/blob_plain/HEAD:/workspace/src/part02.rs) | [next](part03.html)