more fns, remove trait bound in concrete impl

Author: molpopgen

src/traits.rs

@@ -136,6 +136,14 @@ impl private::NewTypeMarker for crate::PopulationId {}
 #[cfg_attr(doc_cfg, doc(cfg(feature = "provenance")))]
 impl private::NewTypeMarker for crate::ProvenanceId {}
 
+/// Interface of a non-ragged table column.
+///
+/// Unlike slice views of table columns, this API
+/// allows indexed via row id types and [`crate::SizeType`].
+///
+/// # Notes
+///
+/// * This trait is sealed.
 pub trait TableColumn<I, T>:
     std::ops::Index<I, Output = T>
     + std::ops::Index<usize, Output = T>
@@ -150,6 +158,14 @@ pub trait TableColumn<I, T>:
     where
         'a: 'b,
         T: 'b;
+
+    fn len(&self) -> usize {
+        self.as_slice().len()
+    }
+
+    fn is_empty(&self) -> bool {
+        self.as_slice().is_empty()
+    }
 }
 
 impl<T> private::TableColumnMarker for crate::table_column::OpaqueTableColumn<'_, T> {}
@@ -167,7 +183,6 @@ where
 impl<I, T> TableColumn<I, T> for crate::table_column::OpaqueTableColumn<'_, T>
 where
     I: private::NewTypeMarker,
-    T: Copy,
 {
     fn as_slice(&self) -> &[T] {
         self.0