global: adding semester + making coarser intervals computed instead of eager

crates/brk_core/src/traits/from_coarser.rs

@@ -0,0 +1,12 @@
+use std::ops::RangeInclusive;
+
+pub trait FromCoarserIndex<T> {
+    fn min_from(coarser: T) -> usize;
+    fn max_from(coarser: T) -> usize;
+    fn inclusive_range_from(coarser: T) -> RangeInclusive<usize>
+    where
+        T: Clone,
+    {
+        Self::min_from(coarser.clone())..=Self::max_from(coarser)
+    }
+}

crates/brk_core/src/traits/mod.rs

@@ -1,3 +1,5 @@
+mod from_coarser;
 mod printable;
 
+pub use from_coarser::*;
 pub use printable::*;