From a00350bc0e82cb5789c3d786b0eb9999e4ba2d70 Mon Sep 17 00:00:00 2001
From: lilymonade <lily.blanleuil@etik.com>
Date: Tue, 11 Mar 2025 22:32:21 +0100
Subject: [PATCH] first draft

---
 practical.yml                      |  7 ++++++
 subject_source/src/lib.rs          |  1 +
 subject_source/src/vec.rs          |  1 +
 subject_source/src/vec/access.rs   | 10 +++++++++
 subject_source/tests/vec_access.rs | 11 ++++++++++
 subject_text/index.md              |  4 ++--
 subject_text/tree                  |  3 +++
 subject_text/vec/index.md          | 34 ++++++++++++++++++++++++++++++
 8 files changed, 69 insertions(+), 2 deletions(-)
 create mode 100644 subject_source/src/vec.rs
 create mode 100644 subject_source/src/vec/access.rs
 create mode 100644 subject_source/tests/vec_access.rs
 create mode 100644 subject_text/vec/index.md

diff --git a/practical.yml b/practical.yml
index c74b803..2988374 100644
--- a/practical.yml
+++ b/practical.yml
@@ -37,3 +37,10 @@ exercises:
       - "get_val_or_panic_ok"
       - "discard_err_ok"
       - "discard_err_err"
+  access:
+    required_files:
+      - "src/vec.rs"
+      - "src/vec/access.rs"
+    tests:
+      - "add_last_two_not_enough"
+      - "add_last_two_enough"
diff --git a/subject_source/src/lib.rs b/subject_source/src/lib.rs
index 629e98f..9eb255a 100644
--- a/subject_source/src/lib.rs
+++ b/subject_source/src/lib.rs
@@ -1 +1,2 @@
 pub mod errors;
+pub mod vec;
diff --git a/subject_source/src/vec.rs b/subject_source/src/vec.rs
new file mode 100644
index 0000000..ce652d9
--- /dev/null
+++ b/subject_source/src/vec.rs
@@ -0,0 +1 @@
+pub mod access; 
diff --git a/subject_source/src/vec/access.rs b/subject_source/src/vec/access.rs
new file mode 100644
index 0000000..16ab63a
--- /dev/null
+++ b/subject_source/src/vec/access.rs
@@ -0,0 +1,10 @@
+/// Add the last two numbers of the input slice.
+///
+/// If the slice is not large enough, return `None`
+/// If it is, return the computed value in a `Some`
+pub fn add_last_two(v: &[f32]) -> Option<f32> {
+    match v.last_chunk() {
+        Some([a, b]) => Some(a + b),
+        None => None,
+    }
+}
diff --git a/subject_source/tests/vec_access.rs b/subject_source/tests/vec_access.rs
new file mode 100644
index 0000000..376a2ee
--- /dev/null
+++ b/subject_source/tests/vec_access.rs
@@ -0,0 +1,11 @@
+use subject_source::vec::access;
+
+#[test]
+pub fn add_last_two_not_enough() {
+    assert_eq!(access::add_last_two(&[1.0]), None);
+}
+
+#[test]
+pub fn add_last_two_enough() {
+    assert_eq!(access::add_last_two(&[1.0, 2.0, 3.0]), Some(5.0));
+}
diff --git a/subject_text/index.md b/subject_text/index.md
index 4e7e358..0fe0647 100644
--- a/subject_text/index.md
+++ b/subject_text/index.md
@@ -1,6 +1,6 @@
 ---
-revision = "0.2.0"
-parts = ["errors"]
+revision = "0.3.0"
+parts = ["errors", "vec"]
 ---
 
 When it comes to programming, it's all fun and games until the real world comes in and sends weird unexpected inputs to your little protege. So you better handle those cases as best as you can. There are 3 main ways of handling errors.
diff --git a/subject_text/tree b/subject_text/tree
index 9681cf5..3f6193c 100644
--- a/subject_text/tree
+++ b/subject_text/tree
@@ -5,4 +5,7 @@
     │   ├── option.rs
     │   └── result.rs
     ├── errors.rs
+    ├── vec
+    │   └── access.rs
+    ├── vec.rs
     └── lib.rs
diff --git a/subject_text/vec/index.md b/subject_text/vec/index.md
new file mode 100644
index 0000000..af20326
--- /dev/null
+++ b/subject_text/vec/index.md
@@ -0,0 +1,34 @@
+---
+name = "Vecs and slices"
+difficulty = 2
+exercises = ["access.md"]
+---
+
+Let's now look at some functions on [`slice`](https://doc.rust-lang.org/std/primitive.slice.html)s and [`Vec`](https://doc.rust-lang.org/std/vec/struct.Vec.html)s. Instead of manualy checking things we will follow the type system using `Option`s and `Result`s we saw earlier.
+
+```note
+Slices (`[T]`) represent some memory space containing an arbitrary number of elements of type `T`. Since they don't have a size known at compilation time, we can only access them through pointers, commonly `&[T]` (references to slices).
+```
+
+```deepening
+`Vec<T>` can be seen as [owned](https://doc.rust-lang.org/book/ch04-00-understanding-ownership.html) `[T]`, it means that every function working on a `&[T]` can work on a `&Vec<T>`.
+```
+
+```prototype
+/// Add the last two numbers of the input slice.
+///
+/// If the slice is not large enough, return `None`
+/// If it is, return the computed value in a `Some`
+pub fn add_last_two(v: &[f32]) -> Option<f32> {
+    unimplemented!()
+}
+```
+
+```example
+fn main() {
+    assert_eq!(add_last_two(&[]), None);
+    assert_eq!(add_last_two(&[10.0]), None);
+    assert_eq!(add_last_two(&[1.0, 2.0, 3.0]), Some(5.0));
+}
+```
+