1 files changed, 12 insertions, 0 deletions
diff --git a/Common/DayPart.lean b/Common/DayPart.lean
new file mode 100644
index 0000000..c6a4d44
--- /dev/null
+++ b/Common/DayPart.lean
@@ -0,0 +1,12 @@
+namespace DayPart
+
+abbrev Days := {d : Nat // d > 0 ∧ d <= 25}
+inductive Parts
+| One
+| Two
+
+class Parse (day : Days) {ι : outParam Type} where
+  parse : String → Option ι
+
+class Part (day : Days) (part : Parts) {ι ρ : outParam Type} [Parse day (ι := ι)] [ToString ρ] where
+  run : ι → Option ρ -- can fail, because it deals with user input...