Mod exercises (foundry-rs#115)

exercises/modules/modules1.cairo

@@ -0,0 +1,30 @@
+// We are writing an app for a restaurant,
+// but take_order functions are not being called correctly.
+// Can you fix this?
+
+// I AM NOT DONE
+
+mod restaurant {
+    fn take_order() -> felt252 {
+        'order_taken'
+    }
+}
+
+#[test]
+fn test_mod_fn() {
+    // Fix this line to call take_order function from module
+    let order_result = take_order();
+
+    assert(order_result == 'order_taken', 'Order not taken');
+}
+
+
+mod tests {
+    #[test]
+    fn test_super_fn() {
+        // Fix this line to call take_order function
+        let order_result = take_order();
+
+        assert(order_result == 'order_taken', 'Order not taken');
+    }
+}

exercises/modules/modules2.cairo

@@ -0,0 +1,56 @@
+// I AM NOT DONE
+// These modules have some issues, can you fix?
+// Run `starklings hint modules2` or `hint` watch command for a hint.
+
+use debug::PrintTrait;
+const YEAR: felt252 = 2050;
+
+mod order {
+    #[derive(Copy, Drop)]
+    struct Order {
+        name: felt252,
+        year: felt252,
+        made_by_phone: bool,
+        made_by_email: bool,
+        item: felt252,
+    }
+
+    fn new_order( name: felt252, made_by_phone: bool, item: felt252 ) -> Order {
+        Order {
+            name,
+            year: YEAR,
+            made_by_phone,
+            made_by_email: ! made_by_phone,
+            item,
+        }
+    }
+}
+
+mod order_utils {
+    fn dummy_phoned_order( name: felt252 ) -> Order {
+        new_order( name, true, 'item_a' )
+    }
+
+    fn dummy_emailed_order( name: felt252 ) -> Order {
+        new_order( name, false, 'item_a' )
+    }
+
+    fn order_fees( order: Order ) -> felt252 {
+        if order.made_by_phone {
+            return 500;
+        }
+
+        200
+    }
+}
+
+#[test]
+fn test_array() {
+    let order1 = order_utils::dummy_phoned_order( 'John Doe' );
+    let fees1 = order_utils::order_fees( order1 );
+    assert( fees1 == 500, 'Order fee should be 500');
+
+    let order2 = order_utils::dummy_emailed_order( 'Jane Doe' );
+    let fees2 = order_utils::order_fees( order2 );
+    assert( fees2 == 200, 'Order fee should be 200');
+}

exercises/modules/readme.md

@@ -0,0 +1,76 @@
+# Modules
+
+Modules allow creating individual scopes and organise your code better. Read about [modules in cairo book](https://cairo-book.github.io/ch06-02-defining-modules-to-control-scope.html).
+
+Here's some code to show modules at play,
+
+## Declaring modules
+
+Modules can be declared in two way,
+
+| Code            | Description                  |
+| --------------- | ---------------------------- |
+| `mod filename;` | Module from a filename.cairo |
+| `mod { ... }`   | Inline module code in braces |
+
+In the exercises we'll use inline modules, but the behaviour is identical.
+
+### `lib.cairo`
+
+```rust
+// Module from a file
+mod restaurant;
+
+fn main() {
+	// ...
+}
+```
+
+### `restaurant.cairo`
+
+```rust
+fn add_to_waitlist() {}
+fn seat_at_table() {}
+
+// Inline modules
+mod serving {
+    fn take_order() {}
+    fn serve_order() {}
+}
+
+mod checkout {
+    fn get_bill() {}
+    fn collect_payment() {}
+}
+```
+
+## Using stuff in modules
+
+| Keyword | Description         | Example                   |
+| ------- | ------------------- | ------------------------- |
+| `super` | Access parent scope | `super::my_module::my_fn` |
+| `use`   | Create shortcuts    | `use my_module::my_fn`    |
+
+### `lib.cairo`
+
+```rust
+// ...
+use restaurant::seat_at_table; // Creates shortcut to seat_at_table
+use restaurant::serving::serve_order; // Another shortcut
+use restaurant::checkout; // Shortcut to a module
+
+
+fn main() {
+	restaurant::add_to_waitlist();
+	seat_at_table(); // Shortcut thanks to use
+
+	restaurant::serving::take_order();
+	serve_order(); // Via shortcut
+}
+
+mod cutomer_checkout {
+	fn start() {
+		super::checkout::collect_payment();
+	}
+}
+```

info.toml

@@ -503,6 +503,23 @@ If you're having trouble updating the distance value in the `Fish` and `Dog` imp
 3. Reconstruct `self` with the updated variables (`self = MyStruct { ... }`) 
 """
 
+# MODULES
+
+[[exercises]]
+name = "modules1"
+path = "exercises/modules/modules1.cairo"
+mode = "test"
+hint = """"""
+
+[[exercises]]
+name = "modules2"
+path = "exercises/modules/modules2.cairo"
+mode = "test"
+hint = """
+While using functions/structs etc from outside the module,
+you can use full paths or `use` keyword to create shortcuts.
+"""
+
 # STARKNET
 
 [[exercises]]