Add generic traits example

noir_by_example/.gitignore

@@ -1,3 +1 @@
 target
-Prover.toml
-Verifier.toml

noir_by_example/Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
     "simple_macros/rust",
-    "loops/rust"
+    "loops/rust",
+    "generic_traits/rust"
 ]
 resolver = "1"

noir_by_example/Nargo.toml

@@ -1,5 +1,6 @@
 [workspace]
 members = [
     "simple_macros/noir",
-    "loops/noir"
+    "loops/noir",
+    "generic_traits/noir"
 ]

noir_by_example/generic_traits/noir/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "generic_traits"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.35.0"
+
+[dependencies]

noir_by_example/generic_traits/noir/Prover.toml

@@ -0,0 +1,2 @@
+cost = "15"
+start = "20"

noir_by_example/generic_traits/noir/src/main.nr

@@ -0,0 +1,84 @@
+// DCI (Data, Context, Interaction) example - keeps objects simple, and binds specific functions to them in their context of use
+
+// ### DATA ###
+struct ValueAccount {
+    balance: u32,
+}
+
+// Primitive functions for data object
+trait ValueFunctions {
+    fn add(&mut self, val: u32);
+    fn sub(&mut self, val: u32);
+}
+
+impl ValueFunctions for ValueAccount {
+    fn add(&mut self, val: u32) {
+        self.balance += val;
+    }
+    fn sub(&mut self, val: u32) {
+        self.balance -= val;
+    }
+}
+
+// ### CONTEXT ###
+
+// Example purchase context
+// Buyer role
+trait Buyer {
+    fn make_payment(&mut self, val: u32);
+}
+
+// impl <T:ValueFunctions> Buyer for T {   // This works in rust
+// impl <T> Buyer for T where T:ValueFunctions { // Valid noir, specifies value functions,
+//    but gives compilation error on line that calls Buyer function make_payment
+impl Buyer for ValueAccount { // context needs to be aware of data object (not just trait)
+    fn make_payment(&mut self, val: u32) {
+        self.sub(val);
+    }
+}
+
+// Seller role
+trait Seller {
+    fn receive_payment(&mut self, val: u32);
+}
+
+impl Seller for ValueAccount {
+    fn receive_payment(&mut self, val: u32) {
+        self.add(val);
+    }
+}
+
+// Define the purchase context with its generic roles
+struct PurchaseContext<B, S> {
+    // Roles
+    buyer: &mut B,
+    seller: &mut S,
+}
+
+impl <B, S> PurchaseContext<B, S> where B: Buyer, S: Seller {
+    fn do_purchase(&mut self, amount: u32) {
+        self.buyer.make_payment(amount); //   Compilation error "No matching impl found for `B: ValueFunctions`" when Buyer uses generic T
+        // self.buyer.receive_payment(amount); // correct compiler error, buyer role cannot receive_payment
+        self.seller.receive_payment(amount);
+    }
+}
+
+// ### INTERACTION ###
+
+fn main(start: u32, cost: pub u32) {
+    assert(start >= cost, "Not enough start balance");
+    // create data object, can use all primitive functions
+    let mut acc1: ValueAccount = ValueAccount { balance: start };
+    let mut acc2: ValueAccount = ValueAccount { balance: start };
+
+    // create context for data object as
+    let mut purchase_context: PurchaseContext<ValueAccount, ValueAccount> = PurchaseContext::<ValueAccount, ValueAccount> { buyer: &mut acc1, seller: &mut acc2 };
+    purchase_context.do_purchase(cost);
+    assert(acc1.balance == start - cost, "Didn't spend");
+    assert(acc2.balance == start + cost, "Didn't receive");
+}
+
+#[test]
+fn test_generic_traits() {
+    main(10, 5);
+}

noir_by_example/generic_traits/rust/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "generic_traits"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

noir_by_example/generic_traits/rust/src/main.rs

@@ -0,0 +1,88 @@
+// DCI (Data, Context, Interaction) example - keeps objects simple, and binds specific functions to them in their context of use
+
+
+// ### DATA ###
+struct ValueAccount {
+    balance: u32,
+}
+
+// Primitive functions for data object
+trait ValueFunctions {
+    fn add(&mut self, val: u32);
+    fn sub(&mut self, val: u32);
+}
+
+impl ValueFunctions for ValueAccount {
+    fn add(&mut self, val: u32) {
+        self.balance += val;
+    }
+    fn sub(&mut self, val: u32) {
+        self.balance -= val;
+    }
+}
+
+
+// ### CONTEXT ###
+
+// Example purchase context
+// Buyer role
+trait Buyer {
+    fn make_payment(&mut self, val: u32);
+}
+
+impl <T:ValueFunctions> Buyer for T {
+    fn make_payment(&mut self, val: u32) {
+        self.sub(val);
+    }
+}
+
+// Seller role
+trait Seller {
+    fn receive_payment(&mut self, val: u32);
+}
+
+impl <T:ValueFunctions> Seller for T {
+    fn receive_payment(&mut self, val: u32) {
+        self.add(val);
+    }
+}
+
+// Define the purchase context with its generic roles
+struct PurchaseContext<'b, 's, B, S> {
+    // Roles
+    buyer: &'b mut B,
+    seller: &'s mut S,
+}
+
+impl <B, S> PurchaseContext<'_, '_, B, S> where B: Buyer, S: Seller {
+    fn do_purchase(&mut self, amount: u32) {
+        self.buyer.make_payment(amount);
+        // self.buyer.receive_payment(amount); // correct compiler error, buyer role cannot receive_payment
+        self.seller.receive_payment(amount);
+    }
+}
+
+
+// ### INTERACTION ###
+
+fn main(start: u32, cost: u32) {
+    assert!(start >= cost, "Not enough start balance");
+    // create data object, can use all primitive functions
+    let mut acc1: ValueAccount = ValueAccount { balance: start };
+    let mut acc2: ValueAccount = ValueAccount { balance: start };
+
+    // create context for data object as
+    let mut purchase_context: PurchaseContext<ValueAccount, ValueAccount> =
+        PurchaseContext::<ValueAccount, ValueAccount> {
+            buyer: &mut acc1, seller: &mut acc2
+        };
+    purchase_context.do_purchase(cost);
+    assert!(acc1.balance == start - cost, "Didn't spend");
+    assert!(acc2.balance == start + cost, "Didn't receive");
+}
+
+
+#[test]
+fn test_generic_traits() {
+    main(10, 5);
+}

noir_by_example/loops/noir/Prover.toml

@@ -0,0 +1 @@
+loop_length = "5"