1 files changed, 21 insertions, 0 deletions
diff --git a/src/Cron/Expr.hs b/src/Cron/Expr.hs
new file mode 100644
index 0000000..a6cb4ca
--- /dev/null
+++ b/src/Cron/Expr.hs
@@ -0,0 +1,21 @@
+module Cron.Expr (Expr (..), StepLExpr (..), showExpr) where
+
+import Data.List.NonEmpty (NonEmpty, intersperse)
+import Data.Semigroup (sconcat)
+import Intro
+
+data Expr = Every | Multi (NonEmpty Int) | Range Int Int | Step StepLExpr Int deriving (Show)
+
+data StepLExpr = StepLEvery | StepLRange Int Int deriving (Show)
+
+showExpr :: Expr -> String
+showExpr = \case
+  Every -> "*"
+  Multi ns -> sconcat $ intersperse "," (fmap show ns)
+  Range n m -> mconcat [show n, "-", show m]
+  Step n m -> mconcat [showStepLExpr n, "/", show m]
+
+showStepLExpr :: StepLExpr -> String
+showStepLExpr = \case
+  StepLEvery -> "*"
+  StepLRange n m -> mconcat [show n, "-", show m]