X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/4f61be32dd480f23a7fef05ee66c42ae27c980c6..77f9c2a913324c4cca010fb5a5e1fa12173e8374:/src/part07.rs?ds=inline diff --git a/src/part07.rs b/src/part07.rs index 6544995..4cc58a4 100644 --- a/src/part07.rs +++ b/src/part07.rs @@ -17,17 +17,17 @@ pub trait Minimum { pub fn vec_min(v: &Vec) -> Option<&T> { let mut min: Option<&T> = None; for e in v { - min = Some(match min { /*@*/ - None => e, /*@*/ - Some(n) => n.min(e) /*@*/ - }); /*@*/ + min = Some(match min { + None => e, + Some(n) => n.min(e) + }); } min } //@ Notice that the return type `Option<&T>` is technically (leaving the borrowing story aside) a //@ pointer to a `T`, that could optionally be invalid. In other words, it's just like a pointer in //@ C(++) or Java that can be `NULL`! However, thanks to `Option` being an `enum`, we cannot forget -//@ to check the pointer for validity, avoiding the safety issues of C(++).
+//@ to check the pointer for validity, avoiding the safety issues of C(++).
//@ Also, if you are worried about wasting space, notice that Rust knows that `&T` can never be //@ `NULL`, and hence optimizes `Option<&T>` to be no larger than `&T`. The `None` case is represented //@ as `NULL`. This is another great example of a zero-cost abstraction: `Option<&T>` is exactly like @@ -35,7 +35,7 @@ pub fn vec_min(v: &Vec) -> Option<&T> { // **Exercise 07.1**: For our `vec_min` to be usable with `BigInt`, you will have to provide an implementation of // `Minimum`. You should be able to pretty much copy the code you wrote for exercise 06.1. You should *not* -// make any copies! +// make any copies of `BigInt`! impl Minimum for BigInt { fn min<'a>(&'a self, other: &'a Self) -> &'a Self { unimplemented!() @@ -62,8 +62,8 @@ impl PartialEq for BigInt { //@ Since implementing `PartialEq` is a fairly mechanical business, you can let Rust automate this //@ by adding the attribute `derive(PartialEq)` to the type definition. In case you wonder about -//@ the "partial", I suggest you check out the documentation of [`PartialEq`](http://doc.rust-lang.org/std/cmp/trait.PartialEq.html) -//@ and [`Eq`](http://doc.rust-lang.org/std/cmp/trait.Eq.html). `Eq` can be automatically derived as well. +//@ the "partial", I suggest you check out the documentation of [`PartialEq`](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html) +//@ and [`Eq`](https://doc.rust-lang.org/std/cmp/trait.Eq.html). `Eq` can be automatically derived as well. // Now we can compare `BigInt`s. Rust treats `PratialEq` special in that it is wired to the operator `==`: //@ That operator can not be used on our numbers! Speaking in C++ terms, we just overloaded the `==` operator @@ -71,7 +71,7 @@ impl PartialEq for BigInt { //@ functions depending on the type of the argument). Instead, one typically finds (or defines) a //@ trait that catches the core characteristic common to all the overloads, and writes a single //@ function that's generic in the trait. For example, instead of overloading a function for all -//@ the ways a string can be represented, one writes a generic functions over [ToString](http://doc.rust-lang.org/std/string/trait.ToString.html). +//@ the ways a string can be represented, one writes a generic functions over [ToString](https://doc.rust-lang.org/std/string/trait.ToString.html). //@ Usually, there is a trait like this that fits the purpose - and if there is, this has the great //@ advantage that any type *you* write, that can convert to a string, just has to implement //@ that trait to be immediately usable with all the functions out there that generalize over `ToString`. @@ -113,7 +113,7 @@ fn test_min() { //@ that users can understand, while `Debug` is meant to show the internal state of data and targeted at //@ the programmer. The latter is what we want for `assert_eq!`, so let's get started. -// All formating is handled by [`std::fmt`](http://doc.rust-lang.org/std/fmt/index.html). I won't explain +// All formating is handled by [`std::fmt`](https://doc.rust-lang.org/std/fmt/index.html). I won't explain // all the details, and refer you to the documentation instead. use std::fmt; @@ -147,4 +147,4 @@ fn test_vec_min() { // of course, need a `Display` bound on `T`.) Then you should be able to use them with `println!` just like you do // with numbers, and get rid of the inherent functions to print `SomethingOrNothing` and `SomethingOrNothing`. -//@ [index](main.html) | [previous](part06.html) | [next](main.html) +//@ [index](main.html) | [previous](part06.html) | [raw source](https://www.ralfj.de/git/rust-101.git/blob_plain/HEAD:/workspace/src/part07.rs) | [next](part08.html)