Alter 4 files

Rename `02-lab.hs` to `lab.hs`
Rename `02-polymorphic_functions.hs` to `polymorphic_functions.hs`
Add `Homework3.hs`
Add `Types.hs`

week3/Homework3.hs

@@ -0,0 +1,21 @@
+-- setting the "warn-incomplete-patterns" flag asks GHC to warn you
+-- about possible missing cases in pattern-matching definitions
+{-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
+
+-- see https://wiki.haskell.org/Safe_Haskell
+{-# LANGUAGE Safe #-}
+
+
+module Homework3 (gasUsage , luhnDouble , luhn) where
+
+import Types
+
+gasUsage :: (Fractional a, Ord a) => a -> Classification
+gasUsage = undefined
+
+luhnDouble :: Int -> Int
+luhnDouble = undefined
+
+luhn :: Int -> Int -> Int -> Int -> Bool
+luhn = undefined
+

week3/Types.hs

@@ -0,0 +1,6 @@
+{-# LANGUAGE StandaloneDeriving, Safe #-}
+
+module Types where
+
+data Classification = Low | Medium | High | SuperHigh deriving (Show, Eq)
+