Implement function pointers.

src/packages/mod.rs

@@ -9,6 +9,7 @@ use crate::stdlib::any::TypeId;
 pub(crate) mod arithmetic;
 mod array_basic;
 mod eval;
+mod fn_basic;
 mod iter_basic;
 mod logic;
 mod map_basic;
@@ -23,6 +24,8 @@ pub use arithmetic::ArithmeticPackage;
 #[cfg(not(feature = "no_index"))]
 pub use array_basic::BasicArrayPackage;
 pub use eval::EvalPackage;
+#[cfg(not(feature = "no_function"))]
+pub use fn_basic::BasicFnPackage;
 pub use iter_basic::BasicIteratorPackage;
 pub use logic::LogicPackage;
 #[cfg(not(feature = "no_object"))]