From 17a1785bbd3efa87995f2e8226aef6763e3c1971 Mon Sep 17 00:00:00 2001
From: Steven <steven.vasilogianis@gmail.com>
Date: Tue, 4 Jun 2019 23:00:01 -0400
Subject: Revert

This reverts commit 0f3dad2819eb6664c44e210308e384ccfc1a402a.
---
 src/Main.hs | 42 +++++++++++++++++-------------------------
 1 file changed, 17 insertions(+), 25 deletions(-)

diff --git a/src/Main.hs b/src/Main.hs
index 4d04d06..190e997 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -18,28 +18,20 @@ solve n = nub $ solveN n
     solveN 1 = solve' [initBoard]
     solveN x = solve' (solveN (x-1))
     solve' bs = concatMap (\bn -> map ((`placeQueen` bn)) (openPositions bn)) bs
-
-initBoard :: Matrix Square
-initBoard = matrix 8 8 (const O)
-
-placeQueen :: (Int, Int) -> Matrix Square -> Matrix Square
-placeQueen p b = setElem Qu p $ markAttacks p b
-
-markAttacks :: (Int, Int) -> Matrix Square -> Matrix Square
-markAttacks p b = markAll positions b
-  where markAll [] mb = mb
-        markAll (mp:mps) mb = let nb = setElem X mp mb
-                              in markAll mps nb
-        positions  = concatMap walk stepDirections
-          where walk dir = takeWhile inBounds $ iterate (dir) $ dir p
-                inBounds (i,j) = i >= 1 && i <= nrows b &&
-                                 j >= 1 && j <= ncols b
-                stepDirections =
-                  let a = (+1); s = subtract 1; k = id -- add; subtract; keep
-                      dirF (fr,fc) = (\(r,c) -> (fr r, fc c))
-                  in map dirF [   (a,k), (s,k)              -- up, down
-                                , (k,a),(k,s)               -- right, left
-                                , (a,a),(a,s),(s,a),(s,s) ] -- diagonals
-
-openPositions :: Matrix Square -> [(Int, Int)]
-openPositions b = [(r,c) | r <- [1..8], c <- [1..8], b ! (r,c) == O ]
+    initBoard = matrix 8 8 (const O)
+    openPositions b = [(i,j) | i <- [1..8], j <- [1..8], b ! (i,j) == O ]
+    placeQueen p b = mark Qu p $ markAttacks b
+      where
+        markAttacks bo = markAll X positions bo
+        positions = concatMap walk directions
+        step (fx,fy) = (\(k,l) -> (fx k, fy l))
+        walk s = takeWhile inBounds $ iterate (step s) $ step s p
+        directions = let a = (+1); s = subtract 1; nc = id
+                     in [   (a,nc),(s,nc)             -- up, down
+                          , (nc,a),(nc,s)             -- right, left
+                          , (a,a),(a,s),(s,a),(s,s) ] -- diags
+        inBounds (i,j) = i >= 1 && i <= nrows b && j >= 1 && j <= ncols b
+        markAll _ [] mb = mb
+        markAll x (mp:mps) mb = let nb = mark x mp mb
+                             in markAll x mps nb
+        mark x mp mb = setElem x mp mb
-- 
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