extend ex01.1 hint

[rust-101.git] / src / part01.rs

diff --git a/src/part01.rs b/src/part01.rs
index 7603c1fa79593467d63c354c293d3bef21b07437..bff079b7db7af065dc04fd95ff371333157dcfe0 100644 (file)
--- a/src/part01.rs
+++ b/src/part01.rs
@@ -9,6 +9,7 @@ use std;
 // terms you write down are not just *statements* (executing code), but *expressions*
 // (returning a value). This applies even to the body of entire functions!
 
+// ## Expression-based programming
 // 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.
@@ -34,16 +35,10 @@ fn number_or_default(n: NumberOrNothing, default: i32) -> i32 {
     }
 }
 
-// With this fresh knowledge, let us now refactor `vec_min`. First of all, we are doing a small change
-// to the type: `&Vec<i32>` denotes a *reference* to a `Vec<i32>`. You can think of this as a pointer
-// (in C terms): Arguments in Rust are passed *by value*, so we need to employ explicit references if
-// that's not what we want. References are per default immutable (like variables), a mutable reference
-// would be denoted `&mut Vec<i32>`.
-fn vec_min(v: &Vec<i32>) -> NumberOrNothing {
+// With this fresh knowledge, let us now refactor `vec_min`.
+fn vec_min(v: Vec<i32>) -> 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.
@@ -61,6 +56,7 @@ fn vec_min(v: &Vec<i32>) -> NumberOrNothing {
 // Now that's already much shorter! Make sure you can go over the code above and actually understand
 // every step of what's going on.
 
+// ## Inherent implementations
 // 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
@@ -85,15 +81,17 @@ impl NumberOrNothing {
 fn read_vec() -> Vec<i32> {
     vec![18,5,7,2,9,27]
 }
-pub fn part_main() {
+pub fn main() {
     let vec = read_vec();
-    let min = vec_min(&vec);
+    let min = vec_min(vec);
     min.print();
 }
 // You will have to replace `part00` by `part01` in the `main` function in
 // `main.rs` to run this code.
 
-// **Exercise**: Write a funtion `vec_avg` that computes the average value of a `Vec<i32>`.
-// *Hint*: `vec.len()` returns the length of a vector `vec`.
+// **Exercise 01.1**: Write a funtion `vec_avg` that computes the average value of a `Vec<i32>` (rounded down to
+// the next integer).
+// 
+// *Hint*: `vec.len() as i32` returns the length of a vector `vec` as signed integer.
 
 // [index](main.html) | [previous](part00.html) | [next](part02.html)