From: Ramakrishnan Muthukrishnan <ram@rkrishnan.org>
Date: Sun, 28 Dec 2014 08:07:21 +0000 (+0530)
Subject: hw11: exercise 1
X-Git-Url: https://git.rkrishnan.org/components/%22news.html/listings/?a=commitdiff_plain;h=2829f5999e1f58bd8f2f7bc1d020bfdb8b9429c0;p=yorgey.git

hw11: exercise 1
---

diff --git a/hw11/SExpr.hs b/hw11/SExpr.hs
index 78ae980..c3f7d70 100644
--- a/hw11/SExpr.hs
+++ b/hw11/SExpr.hs
@@ -10,12 +10,19 @@ import Control.Applicative
 ------------------------------------------------------------
 --  1. Parsing repetitions
 ------------------------------------------------------------
+sequenceA  :: Applicative f => [f a] -> f [a]
+sequenceA [] = pure []
+sequenceA (x:xs) = (:) <$> x <*> sequenceA xs
+-- sequenceA (x:xs) = liftA2 (:) x (sequenceA xs)
+
+replicateA :: Applicative f => Int -> f a -> f [a]
+replicateA n x = sequenceA (replicate n x)
 
 zeroOrMore :: Parser a -> Parser [a]
-zeroOrMore p = undefined
+zeroOrMore p = oneOrMore p <|> pure []
 
 oneOrMore :: Parser a -> Parser [a]
-oneOrMore p = undefined
+oneOrMore p = liftA2 (:) p (zeroOrMore p)
 
 ------------------------------------------------------------
 --  2. Utilities