be more explicit about dereferencing

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

diff --git a/workspace/src/part01.rs b/workspace/src/part01.rs
index da94915e48523e39d35299217973710254e08fc0..ed6717ca3b8111f7b61afc56f0b863c6f3fffc73 100644 (file)
--- a/workspace/src/part01.rs
+++ b/workspace/src/part01.rs
@@ -1,28 +1,17 @@
-// ***Remember to enable/add this part in `main.rs`!***
-
 // Rust-101, Part 01: Expressions, Inherent methods
 // ================================================
 
-// Even though our code from the first part works, we can still learn a
-// lot by making it prettier. To understand how, it is important to
-// 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 Rust to compile this file, make sure to enable the corresponding line
+// in `main.rs` before going on.
+
 
 // ## 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.
-// 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 } }
 
-// And the same applies to case distinction with `match`: Every `arm` of the match
-// gives the expression that is returned in the respective case.
-// (We repeat the definition from the previous part here.)
 enum NumberOrNothing {
     Number(i32),
     Nothing
@@ -35,28 +24,22 @@ fn number_or_default(n: NumberOrNothing, default: i32) -> i32 {
     }
 }
 
+// It is even the case that blocks are expressions, evaluating to the last expression they contain.
+fn compute_stuff(x: i32) -> i32 {
+    let y = { let z = x*x; z + 14 };
+    y*y
+}
+
 // Let us now refactor `vec_min`.
 fn vec_min(v: Vec<i32>) -> NumberOrNothing {
-    // Remember that helper function `min_i32`? Rust allows us to define such helper functions *inside* other
-    // functions. This is just a matter of namespacing, the inner function has no access to the data of the outer
-    // one. Still, being able to nicely group functions can be very useful.
     fn min_i32(a: i32, b: i32) -> i32 {
-        if a < b { a } else { b }
+        unimplemented!()
     }
 
     let mut min = Nothing;
     for e in v {
-        // 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.
-        min = Number(match min {
-            Nothing => e,
-            Number(n) => min_i32(n, e)
-        });
+        unimplemented!()
     }
-    // The `return` keyword exists in Rust, but it is rarely used. Instead, we typically
-    // make use of the fact that the entire function body is an expression, so we can just
-    // write down the desired return value.
     min
 }
 
@@ -64,10 +47,6 @@ fn vec_min(v: Vec<i32>) -> NumberOrNothing {
 // 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
-// by providing an *inherent implementation*.
 impl NumberOrNothing {
     fn print(self) {
         match self {
@@ -76,13 +55,6 @@ impl NumberOrNothing {
         };
     }
 }
-// So, what just happened? Rust separates code from data, so the definition of the
-// methods on an `enum` (and also on `struct`, which we will learn about later)
-// 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:
 fn read_vec() -> Vec<i32> {
@@ -91,7 +63,7 @@ fn read_vec() -> Vec<i32> {
 pub fn main() {
     let vec = read_vec();
     let min = vec_min(vec);
-    min.print();
+    unimplemented!()
 }
 // You will have to replace `part00` by `part01` in the `main` function in
 // `main.rs` to run this code.
@@ -100,4 +72,3 @@ pub fn main() {
 
 // **Exercise 01.2**: Write a function `vec_print` that takes a vector and prints all its elements.
 
-// [index](main.html) | [previous](part00.html) | [next](part02.html)