Support equality on multidimensional arrays

Author: BCSharp

Src/IronPython/Runtime/Operations/ArrayOps.cs

@@ -93,10 +93,38 @@ public static object __eq__(CodeContext context, Array self, [NotNone] Array oth
             if (other is null) throw PythonOps.TypeError("expected Array, got None");
 
             if (self.GetType() != other.GetType()) return ScriptingRuntimeHelpers.False;
+            // same type implies: same rank, same element type
+            for (int d = 0; d < self.Rank; d++) {
+                if (self.GetLowerBound(d) != other.GetLowerBound(d)) return ScriptingRuntimeHelpers.False;
+                if (self.GetUpperBound(d) != other.GetUpperBound(d)) return ScriptingRuntimeHelpers.False;
+            }
+            if (self.Length == 0) return ScriptingRuntimeHelpers.True; // fast track
 
-            return ScriptingRuntimeHelpers.BooleanToObject(
-                ((IStructuralEquatable)self).Equals(other, context.LanguageContext.EqualityComparerNonGeneric)
-            );
+            if (self.Rank == 1 && self.GetLowerBound(0) == 0 ) {
+                // IStructuralEquatable.Equals only works for 1-dim, 0-based arrays
+                return ScriptingRuntimeHelpers.BooleanToObject(
+                    ((IStructuralEquatable)self).Equals(other, context.LanguageContext.EqualityComparerNonGeneric)
+                );
+            } else {
+                int[] ix = new int[self.Rank];
+                for (int d = 0; d < self.Rank; d++) {
+                    ix[d] = self.GetLowerBound(d);
+                }
+                for (int i = 0; i < self.Length; i++) {
+                    if (!PythonOps.EqualRetBool(self.GetValue(ix), other.GetValue(ix))) {
+                        return ScriptingRuntimeHelpers.False;
+                    }
+                    for (int d = self.Rank - 1; d >= 0; d--) {
+                        if (ix[d] < self.GetUpperBound(d)) {
+                            ix[d]++;
+                            break;
+                        } else {
+                            ix[d] = self.GetLowerBound(d);
+                        }
+                    }
+                }
+                return ScriptingRuntimeHelpers.True;
+            }
         }
 
         [StaticExtensionMethod]

Tests/test_array.py

@@ -318,4 +318,51 @@ def test_equality(self):
         self.assertTrue(a != l)
         self.assertTrue(l != a)
 
+    def test_equality_base(self):
+        a = System.Array.CreateInstance(int, (5,), (5,))
+        a2 = System.Array.CreateInstance(int, (5,), (5,))
+        b = System.Array.CreateInstance(int, (6,), (5,))
+        c = System.Array.CreateInstance(int, (5,), (6,))
+        d = System.Array.CreateInstance(int, (6,), (6,))
+
+        self.assertTrue(a == a2)
+        self.assertFalse(a == b)
+        self.assertFalse(a == c)
+        self.assertFalse(a == d)
+
+        self.assertFalse(a != a2)
+        self.assertTrue(a != b)
+        self.assertTrue(a != c)
+        self.assertTrue(a != d)
+
+    def test_equality_rank(self):
+        a = System.Array.CreateInstance(int, 5, 6)
+        a2 = System.Array.CreateInstance(int, 5, 6)
+        b = System.Array.CreateInstance(int, 5, 6)
+        b[0, 0] = 1
+        c = System.Array.CreateInstance(int, (6, 5), (0, 0))
+        c[0, 0] = 1
+        d = System.Array.CreateInstance(int, (6, 5), (1, 1))
+        d[1, 1] = 1
+        d1 = System.Array.CreateInstance(int, (6, 5), (1, 1))
+        d1[1, 1] = 1
+
+        self.assertTrue(a == a2)
+        self.assertFalse(a == b) # different element
+        self.assertFalse(a == c) # different rank
+        self.assertFalse(a == d) # different rank
+        self.assertFalse(b == c) # different shape
+        self.assertFalse(b == d) # different shape & base
+        self.assertFalse(c == d) # different base
+        self.assertTrue(d == d1)
+
+        self.assertFalse(a != a2)
+        self.assertTrue(a != b)
+        self.assertTrue(a != c)
+        self.assertTrue(a != d)
+        self.assertTrue(b != c)
+        self.assertTrue(b != d)
+        self.assertTrue(c != d)
+        self.assertFalse(d != d1)
+
 run_test(__name__)