3 files changed, 21 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...
diff --git a/Common/Helpers.lean b/Common/Helpers.lean
new file mode 100644
index 0000000..f57f826
--- /dev/null
+++ b/Common/Helpers.lean
@@ -0,0 +1,2 @@
+def curry (g : (α × β) → γ) : α → β → γ := λ a b ↦ g (a,b)
+def uncurry (f : α → β → γ) : (α × β) → γ := λ (a,b) ↦ f a b
diff --git a/Common/Option.lean b/Common/Option.lean
new file mode 100644
index 0000000..23ea8d6
--- /dev/null
+++ b/Common/Option.lean
@@ -0,0 +1,7 @@
+namespace Option
+
+def zip (a : Option α) (b : Option β) : Option (α×β) := a >>= λ a ↦ b >>= λ b ↦ (a,b)
+
+def unzip : (a : Option (α×β)) → (Option α) × (Option β)
+| none => (none, none)
+| some (a, b) => (some a, some b)