Refactor random number generation to factory

- Use a `make-random` factory to create isolated random number
  generators.
- Remove the global `prng` from the `Environment`.
- Ensure `make-random` can be called with or without a seed.

examples/pipeline_script_ticker.myc

@@ -1,10 +1,10 @@
-;; Benchmark: 2.0us
-;; Benchmark-Repeat: 1015
+;; Benchmark: 3.0us
+;; Benchmark-Repeat: 593
 ;; Output: PipelineNode[last: Some(110.45243843391206)]
 
 (do
   ;; Set the random seed to match the existing test output exactly
-  (seed! 42)
+  (def random (make-random 42))
 
   ;; Use our new generic create-ticker to pulse 3 times
   (def cnt 3)

src/ast/environment.rs

@@ -28,7 +28,6 @@ pub struct Environment {
     pub global_types: Rc<RefCell<HashMap<GlobalIdx, StaticType>>>,
     pub global_purity: Rc<RefCell<HashMap<GlobalIdx, Purity>>>,
     pub global_values: Rc<RefCell<Vec<Value>>>,
-    pub prng: Rc<RefCell<fastrand::Rng>>,
     pub function_registry: Rc<RefCell<HashMap<GlobalIdx, BoundNode>>>,
     pub typed_function_registry: Rc<RefCell<HashMap<GlobalIdx, AnalyzedNode>>>,
     pub monomorph_cache: Rc<RefCell<MonoCache>>,
@@ -102,7 +101,6 @@ impl Environment {
             global_types: Rc::new(RefCell::new(HashMap::new())),
             global_purity: Rc::new(RefCell::new(HashMap::new())),
             global_values: Rc::new(RefCell::new(Vec::new())),
-            prng: Rc::new(RefCell::new(fastrand::Rng::new())),
             function_registry: Rc::new(RefCell::new(HashMap::new())),
             typed_function_registry: Rc::new(RefCell::new(HashMap::new())),
             monomorph_cache: Rc::new(RefCell::new(HashMap::new())),

src/ast/rtl/math.rs

@@ -135,27 +135,39 @@ pub fn register(env: &Environment) {
         best
     });
 
-    // Random
-    let random_ty = StaticType::Function(Box::new(Signature {
+    // Random generator factory (Closure-based)
+    let generator_sig = Signature {
         params: StaticType::Tuple(vec![]),
         ret: StaticType::Float,
-    }));
+    };
     
-    let prng = env.prng.clone();
-    env.register_native_fn("random", random_ty, Purity::SideEffectFree, move |_| {
-        Value::Float(prng.borrow_mut().f64())
-    });
+    let make_random_ty = StaticType::FunctionOverloads(vec![
+        Signature {
+            params: StaticType::Tuple(vec![]),
+            ret: StaticType::Function(Box::new(generator_sig.clone())),
+        },
+        Signature {
+            params: StaticType::Tuple(vec![StaticType::Int]),
+            ret: StaticType::Function(Box::new(generator_sig)),
+        },
+    ]);
 
-    let seed_ty = StaticType::Function(Box::new(Signature {
-        params: StaticType::Tuple(vec![StaticType::Int]),
-        ret: StaticType::Void,
-    }));
+    env.register_native_fn("make-random", make_random_ty, Purity::SideEffectFree, |args| {
+        let rng = if args.is_empty() {
+            fastrand::Rng::new()
+        } else if let Value::Int(s) = args[0] {
+            fastrand::Rng::with_seed(s as u64)
+        } else {
+            fastrand::Rng::new()
+        };
         
-    let prng_seed = env.prng.clone();
-    env.register_native_fn("seed!", seed_ty, Purity::Impure, move |args| {
-        if let Value::Int(s) = args[0] {
-            prng_seed.borrow_mut().seed(s as u64);
-        }
-        Value::Void
+        let prng = std::rc::Rc::new(std::cell::RefCell::new(rng));
+        
+        Value::Function(std::rc::Rc::new(crate::ast::types::NativeFunction {
+            func: std::rc::Rc::new(move |_| {
+                Value::Float(prng.borrow_mut().f64())
+            }),
+            purity: Purity::Impure,
+        }))
     });
 }

src/integration_test.rs

@@ -175,12 +175,13 @@ mod tests {
         let env1 = Environment::new();
         let env2 = Environment::new();
 
-        // 1. Seed env1
-        env1.run_script("(seed! 123)").unwrap();
-        let val1_a = env1.run_script("(random)").unwrap();
+        // 1. Create a seeded generator in env1
+        env1.run_script("(def rand (make-random 123))").unwrap();
+        let val1_a = env1.run_script("(rand)").unwrap();
 
-        // 2. env2 should have its own default seed state
-        let val2_a = env2.run_script("(random)").unwrap();
+        // 2. env2 should have its own default seed state for its generators
+        env2.run_script("(def rand (make-random))").unwrap();
+        let val2_a = env2.run_script("(rand)").unwrap();
 
         // They are highly unlikely to be equal by default,
         // and seeding env1 MUST not have seeded env2.
@@ -189,9 +190,9 @@ mod tests {
             "Environments must have isolated PRNG states"
         );
 
-        // 3. Seed env2 differently
-        env2.run_script("(seed! 123)").unwrap();
-        let val2_b = env2.run_script("(random)").unwrap();
+        // 3. Create another generator in env2 with the same seed
+        env2.run_script("(def rand-same (make-random 123))").unwrap();
+        let val2_b = env2.run_script("(rand-same)").unwrap();
 
         // After same seeding, they should match (isolated but identical seed)
         assert_eq!(
@@ -205,12 +206,12 @@ mod tests {
         let env = Environment::new();
 
         // 1. First run with seed 42
-        env.run_script("(seed! 42)").unwrap();
-        let val1 = env.run_script("(random)").unwrap();
+        env.run_script("(def rand1 (make-random 42))").unwrap();
+        let val1 = env.run_script("(rand1)").unwrap();
 
         // 2. Second run with same seed 42
-        env.run_script("(seed! 42)").unwrap();
-        let val2 = env.run_script("(random)").unwrap();
+        env.run_script("(def rand2 (make-random 42))").unwrap();
+        let val2 = env.run_script("(rand2)").unwrap();
 
         assert_eq!(
             val1, val2,
@@ -218,8 +219,8 @@ mod tests {
         );
 
         // 3. Third run with different seed
-        env.run_script("(seed! 123)").unwrap();
-        let val3 = env.run_script("(random)").unwrap();
+        env.run_script("(def rand3 (make-random 123))").unwrap();
+        let val3 = env.run_script("(rand3)").unwrap();
         assert_ne!(val1, val3, "Random results must differ for different seeds");
     }