From e69710027d85a2d644d28e3e526330ad171d9983 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Sat, 27 Aug 2011 20:04:20 -0400
Subject: [PATCH] Make cube_at either return a cube or error instead of
 returning a (Maybe Cube).

---
 src/Grid.hs       | 52 +++++++++++++++++++++++++-------------------
 src/Tests/Grid.hs | 55 +++++++++++++++++++++++------------------------
 2 files changed, 57 insertions(+), 50 deletions(-)

diff --git a/src/Grid.hs b/src/Grid.hs
index 8ce2430..7996319 100644
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -4,6 +4,7 @@
 module Grid
 where
 
+import qualified Data.Array.Repa as R
 import Test.QuickCheck (Arbitrary(..), Gen, Positive(..))
 
 import Cube (Cube(Cube), find_containing_tetrahedra)
@@ -12,7 +13,6 @@ import Point (Point)
 import Tetrahedron (polynomial)
 import Values (Values3D, dims, empty3d, zoom_shape)
 
-import qualified Data.Array.Repa as R
 
 -- | Our problem is defined on a Grid. The grid size is given by the
 --   positive number h. The function values are the values of the
@@ -59,17 +59,26 @@ cubes g
 
 -- | Takes a grid and a position as an argument and returns the cube
 --   centered on that position. If there is no cube there (i.e. the
---   position is outside of the grid), it will return 'Nothing'.
-cube_at :: Grid -> Int -> Int -> Int -> Maybe Cube
+--   position is outside of the grid), it will throw an error.
+cube_at :: Grid -> Int -> Int -> Int -> Cube
 cube_at g i j k
-    | i < 0 = Nothing
-    | j < 0 = Nothing
-    | k < 0 = Nothing
-    | k >= length (cubes g) = Nothing
-    | j >= length ((cubes g) !! k) = Nothing
-    | i >= length (((cubes g) !! k) !! j) = Nothing
-    | otherwise = Just $ (((cubes g) !! k) !! j) !! i
-
+    | i < 0 = error "i < 0 in cube_at"
+    | j < 0 = error "j < 0 in cube_at"
+    | k < 0 = error "k < 0 in cube_at"
+    | otherwise =
+        let zsize = length (cubes g) in
+          if k >= zsize then
+            error "k >= xsize in cube_at"
+          else
+            let ysize = length ((cubes g) !! k) in
+              if j >= ysize then
+                error "j >= ysize in cube_at"
+              else
+                let xsize = length (((cubes g) !! k) !! j) in
+                  if i >= xsize then
+                    error "i >= xsize in cube_at"
+                  else
+                    (((cubes g) !! k) !! j) !! i
 
 
 --   The first cube along any axis covers (-h/2, h/2). The second
@@ -96,9 +105,7 @@ calculate_containing_cube_coordinate g coord
 --   to check every cube.
 find_containing_cube :: Grid -> Point -> Cube
 find_containing_cube g p =
-    case cube_at g i j k of
-      Just c -> c
-      Nothing -> error "No cube contains the given point."
+    cube_at g i j k
     where
       (x, y, z) = p
       i = calculate_containing_cube_coordinate g x
@@ -107,18 +114,19 @@ find_containing_cube g p =
 
 
 {-# INLINE zoom_lookup #-}
-zoom_lookup :: Grid -> a -> (R.DIM3 -> Double)
-zoom_lookup g _ = zoom_result g
+zoom_lookup :: Grid -> Int -> a -> (R.DIM3 -> Double)
+zoom_lookup g scale_factor _ = zoom_result g scale_factor
 
 
 {-# INLINE zoom_result #-}
-zoom_result :: Grid -> R.DIM3 -> Double
-zoom_result g (R.Z R.:. i R.:. j R.:. k) =
+zoom_result :: Grid -> Int -> R.DIM3 -> Double
+zoom_result g scale_factor (R.Z R.:. i R.:. j R.:. k) =
   f p
   where
-    i' = fromIntegral i
-    j' = fromIntegral j
-    k' = fromIntegral k
+    sf = fromIntegral scale_factor
+    i' = fromIntegral i / sf
+    j' = fromIntegral j / sf
+    k' = fromIntegral k / sf
     p  = (i', j', k') :: Point
     c = find_containing_cube g p
     t = head (find_containing_tetrahedra c p)
@@ -129,7 +137,7 @@ zoom :: Grid -> Int -> Values3D
 zoom g scale_factor
     | xsize == 0 || ysize == 0 || zsize == 0 = empty3d
     | otherwise =
-        R.force $ R.traverse arr transExtent (zoom_lookup g)
+        R.force $ R.traverse arr transExtent (zoom_lookup g scale_factor)
           where
             arr = function_values g
             (xsize, ysize, zsize) = dims arr
diff --git a/src/Tests/Grid.hs b/src/Tests/Grid.hs
index 92ba20e..3cc316a 100644
--- a/src/Tests/Grid.hs
+++ b/src/Tests/Grid.hs
@@ -1,7 +1,6 @@
 module Tests.Grid
 where
 
-import Data.Maybe (fromJust)
 import Test.HUnit
 
 import Assertions
@@ -23,7 +22,7 @@ test_trilinear_c0030 =
     assertAlmostEqual "c0030 is correct" (c t 0 0 3 0) (17/8)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -35,7 +34,7 @@ test_trilinear_c0003 =
     assertAlmostEqual "c0003 is correct" (c t 0 0 0 3) (27/8)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -47,7 +46,7 @@ test_trilinear_c0021 =
     assertAlmostEqual "c0021 is correct" (c t 0 0 2 1) (61/24)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -59,7 +58,7 @@ test_trilinear_c0012 =
     assertAlmostEqual "c0012 is correct" (c t 0 0 1 2) (71/24)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -71,7 +70,7 @@ test_trilinear_c0120 =
     assertAlmostEqual "c0120 is correct" (c t 0 1 2 0) (55/24)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -83,7 +82,7 @@ test_trilinear_c0102 =
     assertAlmostEqual "c0102 is correct" (c t 0 1 0 2) (73/24)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -95,7 +94,7 @@ test_trilinear_c0111 =
     assertAlmostEqual "c0111 is correct" (c t 0 1 1 1) (8/3)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -107,7 +106,7 @@ test_trilinear_c0210 =
     assertAlmostEqual "c0210 is correct" (c t 0 2 1 0) (29/12)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -119,7 +118,7 @@ test_trilinear_c0201 =
     assertAlmostEqual "c0201 is correct" (c t 0 2 0 1) (11/4)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -131,7 +130,7 @@ test_trilinear_c0300 =
     assertAlmostEqual "c0300 is correct" (c t 0 3 0 0) (5/2)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -143,7 +142,7 @@ test_trilinear_c1020 =
     assertAlmostEqual "c1020 is correct" (c t 1 0 2 0) (8/3)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -155,7 +154,7 @@ test_trilinear_c1002 =
     assertAlmostEqual "c1002 is correct" (c t 1 0 0 2) (23/6)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -167,7 +166,7 @@ test_trilinear_c1011 =
     assertAlmostEqual "c1011 is correct" (c t 1 0 1 1) (13/4)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -179,7 +178,7 @@ test_trilinear_c1110 =
     assertAlmostEqual "c1110 is correct" (c t 1 1 1 0) (23/8)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -191,7 +190,7 @@ test_trilinear_c1101 =
     assertAlmostEqual "c1101 is correct" (c t 1 1 0 1) (27/8)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -203,7 +202,7 @@ test_trilinear_c1200 =
     assertAlmostEqual "c1200 is correct" (c t 1 2 0 0) 3
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -215,7 +214,7 @@ test_trilinear_c2010 =
     assertAlmostEqual "c2010 is correct" (c t 2 0 1 0) (10/3)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -227,7 +226,7 @@ test_trilinear_c2001 =
     assertAlmostEqual "c2001 is correct" (c t 2 0 0 1) 4
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -239,7 +238,7 @@ test_trilinear_c2100 =
     assertAlmostEqual "c2100 is correct" (c t 2 1 0 0) (7/2)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -251,7 +250,7 @@ test_trilinear_c3000 =
     assertAlmostEqual "c3000 is correct" (c t 3 0 0 0) 4
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -263,7 +262,7 @@ test_trilinear_f0_t0_v0 =
     assertEqual "v0 is correct" (v0 t) (1, 1, 1)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -275,7 +274,7 @@ test_trilinear_f0_t0_v1 =
     assertEqual "v1 is correct" (v1 t) (0.5, 1, 1)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -287,7 +286,7 @@ test_trilinear_f0_t0_v2 =
     assertEqual "v2 is correct" (v2 t) (0.5, 0.5, 1.5)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -299,7 +298,7 @@ test_trilinear_f0_t0_v3 =
     assertClose "v3 is correct" (v3 t) (0.5, 1.5, 1.5)
       where
         g = make_grid 1 trilinear
-        cube = fromJust $ cube_at g 1 1 1
+        cube = cube_at g 1 1 1
         t = tetrahedron0 cube
 
 
@@ -317,7 +316,7 @@ test_trilinear_reproduced =
                       let k' = fromIntegral k]
     where
       g = make_grid 1 trilinear
-      c0 = fromJust $ cube_at g 1 1 1
+      c0 = cube_at g 1 1 1
 
 
 test_zeros_reproduced :: Assertion
@@ -332,7 +331,7 @@ test_zeros_reproduced =
                       let k' = fromIntegral k]
     where
       g = make_grid 1 zeros
-      c0 = fromJust $ cube_at g 1 1 1
+      c0 = cube_at g 1 1 1
       t0 = tetrahedron0 c0
       p = polynomial t0
 
@@ -352,7 +351,7 @@ test_trilinear9x9x9_reproduced =
               let k' = (fromIntegral k) * 0.5]
     where
       g = make_grid 1 trilinear
-      c0 = fromJust $ cube_at g 1 1 1
+      c0 = cube_at g 1 1 1
 
 
 -- | The point 'p' in this test lies on the boundary of tetrahedra 12 and 15.
-- 
2.43.2