Generic accumulators

1 files changed, 9 insertions, 0 deletions

diff --git a/src/Data.hs b/src/Data.hs
index 8c39c6c..eb6c033 100644
--- a/src/Data.hs
+++ b/src/Data.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE QuantifiedConstraints #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 module Data where
 
@@ -25,6 +26,14 @@ sappend :: SList f l1 -> SList f l2 -> SList f (Append l1 l2)
 sappend SNil l = l
 sappend (SCons x xs) l = SCons x (sappend xs l)
 
+type family Replicate n x where
+  Replicate Z x = '[]
+  Replicate (S n) x = x : Replicate n x
+
+sreplicate :: SNat n -> f t -> SList f (Replicate n t)
+sreplicate SZ _ = SNil
+sreplicate (SS n) x = x `SCons` sreplicate n x
+
 data Nat = Z | S Nat
   deriving (Show, Eq, Ord)