add boolean cast function

src/stl.rs

@@ -162,6 +162,17 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         },
     );
 
+    syms.insert(
+        "bool".to_string(),
+        Symbol {
+            name: String::from("bool"),
+            args: Args::Infinite,
+            conditional_branches: false,
+            docs: boolean::BOOLCAST_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(boolean::boolcast_callback)),
+        },
+    );
+
     syms.insert(
         "or".to_string(),
         Symbol {