Added tests and fixed some issues

src/compiler/prelude.rs

@@ -1475,8 +1475,7 @@ impl Compiler {
                                                                             "emit" => "op_accept",
                                                                             "children" =>
                                                                                 (value!([
-                                                                                    "emit" => "value_integer",
-                                                                                    "value" => 0
+                                                                                    "emit" => "value_void"
                                                                                 ]))
                                                                         ]))
                                                                     ]))

src/prelude.tok

@@ -148,6 +148,6 @@ avg : @value {
         cnt++
     }
 
-    if !cnt return 0
+    if !cnt return void
     res / cnt
 }

src/value/iter/iter.rs

@@ -97,7 +97,7 @@ impl Iter {
         let mut borrowed_iter = iter.borrow_mut();
 
         if let Some(iter) = borrowed_iter.object_mut::<Iter>() {
-            Ok(iter.max().unwrap())
+            Ok(iter.max().unwrap_or(RefValue::from(Value::Void)))
         } else {
             Ok(iter.clone())
         }
@@ -107,7 +107,7 @@ impl Iter {
         let mut borrowed_iter = iter.borrow_mut();
 
         if let Some(iter) = borrowed_iter.object_mut::<Iter>() {
-            Ok(iter.min().unwrap())
+            Ok(iter.min().unwrap_or(RefValue::from(Value::Void)))
         } else {
             Ok(iter.clone())
         }

tests/aggregates.tok

@@ -0,0 +1,36 @@
+#testmode:repl
+# Aggregate Functions
+
+l = list(range(10))
+
+min(l)
+max(l)
+sum(l)
+avg(l)
+
+min(42)
+max(42)
+sum(42)
+avg(42)
+
+print(type(min(void)))
+print(type(max(void)))
+print(type(sum(void)))
+print(type(avg(void)))
+
+
+#---
+#0
+#9
+#45
+#4.5
+
+#42
+#42
+#42
+#42
+
+#void
+#void
+#void
+#void