From 22129a2fcb660a29e1ed6935713282bc78c8d62f Mon Sep 17 00:00:00 2001
From: cyfraeviolae <cyfraeviolae>
Date: Sun, 30 May 2021 16:47:16 -0400
Subject: associativity for -> and <->

---
 src/Parser.hs | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/Parser.hs b/src/Parser.hs
index e328b6e..0891481 100644
--- a/src/Parser.hs
+++ b/src/Parser.hs
@@ -79,16 +79,9 @@ pMultiMatOp s op = do
     Parsec.sepBy1
       pFormulaInner
       (Parsec.space *> Parsec.string s *> Parsec.space)
-  return $ foldl1 op (term : terms)
-
-pBinMatOp :: String -> (Formula -> Formula -> Formula) -> Parser Formula
-pBinMatOp s op = do
-  x <- pFormulaInner
-  _ <- Parsec.space
-  _ <- Parsec.string s
-  _ <- Parsec.space
-  y <- pFormulaInner
-  return $ op x y
+  -- Imp is right-associative, whereas And/Or/Iff can be either, so
+  -- use right-associative for everything.
+  return $ foldr1 op (term : terms)
 
 pNot :: Parser Formula
 pNot = Not <$> (Parsec.char '~' *> pFormulaInner)
@@ -115,8 +108,8 @@ pFormulaInner =
       (Parsec.char ')')
       ( Parsec.try (pMultiMatOp "&" And)
           <|> Parsec.try (pMultiMatOp "|" Or)
-          <|> Parsec.try (pBinMatOp "<->" Iff)
-          <|> Parsec.try (pBinMatOp "->" Imp)
+          <|> Parsec.try (pMultiMatOp "<->" Iff)
+          <|> Parsec.try (pMultiMatOp "->" Imp)
       )
     <|> Parsec.try pQuantifier
 
-- 
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