X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/53260b4082f1c76b657845560c273b853a166fab..f21475ab3d58a70db564410f2b81572a4dbb492c:/src/part01.rs diff --git a/src/part01.rs b/src/part01.rs index 7c205bd..927a617 100644 --- a/src/part01.rs +++ b/src/part01.rs @@ -8,13 +8,13 @@ use std; // understand that Rust is an "expression-based" language. This means that most of the // terms you write down are not just *statements* (executing code), but *expressions* // (returning a value). This applies even to the body of entire functions! -// + // For example, consider `sqr`: fn sqr(i: i32) -> i32 { i * i } // Between the curly braces, we are giving the *expression* that computes the return value. // So we can just write `i * i`, the expression that returns the square if `i`! // This is very close to how mathematicians write down functions (but with more types). -// + // Conditionals are also just expressions. You can compare this to the ternary `? :` operator // from languages like C. fn abs(i: i32) -> i32 { if i >= 0 { i } else { -i } } @@ -42,10 +42,11 @@ fn number_or_default(n: NumberOrNothing, default: i32) -> i32 { fn vec_min(v: &Vec) -> NumberOrNothing { let mut min = Nothing; for e in v { + // Now that `v` is just a reference, the same goes for `e`, so we have to dereference the pointer. let e = *e; // Notice that all we do here is compute a new value for `min`, and that it will always end // up being a `Number` rather than `Nothing`. In Rust, the structure of the code - // can express this uniformity as follows: + // can express this uniformity. min = Number(match min { Nothing => e, Number(n) => std::cmp::min(n, e) @@ -63,7 +64,7 @@ fn vec_min(v: &Vec) -> NumberOrNothing { // So much for `vec_min`. Let us now reconsider `print_number_or_nothing`. That function // really belongs pretty close to the type `NumberOrNothing`. In C++ or Java, you would // probably make it a method of the type. In Rust, we can achieve something very similar -// by providing an *inherent implementation* as follows: +// by providing an *inherent implementation*. impl NumberOrNothing { fn print(self) { match self { @@ -77,7 +78,7 @@ impl NumberOrNothing { // is independent of the definition of the type. `self` is like `this` in other // languages, and its type is always implicit. So `print` is now a method that // takes as first argument a `NumberOrNothing`, just like `print_number_or_nothing`. -// +// // Try making `number_or_default` from above an inherent method as well! // With our refactored functions and methods, `main` now looks as follows: @@ -93,6 +94,7 @@ pub fn part_main() { // `main.rs` to run this code. // **Exercise**: Write a funtion `vec_avg` that computes the average value of a `Vec`. +// // *Hint*: `vec.len()` returns the length of a vector `vec`. // [index](main.html) | [previous](part00.html) | [next](part02.html)