Implement equality comparisons on System.Array (#1821)

* Implement equality comparisons on System.Array

* Support equality on multidimensional arrays

Src/IronPython/Runtime/Operations/ArrayOps.cs

@@ -87,6 +87,58 @@ public static object __new__(CodeContext context, PythonType pythonType, object
             return res;
         }
 
+        [StaticExtensionMethod]
+        public static object __eq__(CodeContext context, Array self, [NotNone] Array other) {
+            if (self is null) throw PythonOps.TypeError("expected Array, got None");
+            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
+
+            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]
+        [return: MaybeNotImplemented]
+        public static object __eq__(CodeContext context, object self, object? other) => NotImplementedType.Value;
+
+        [StaticExtensionMethod]
+        public static object __ne__(CodeContext context, Array self, [NotNone] Array other)
+            => ScriptingRuntimeHelpers.BooleanToObject(ReferenceEquals(__eq__(context, self, other), ScriptingRuntimeHelpers.False));
+
+        [StaticExtensionMethod]
+        [return: MaybeNotImplemented]
+        public static object __ne__(CodeContext context, object self, object? other) => NotImplementedType.Value;
+
         /// <summary>
         /// Multiply two object[] arrays - slow version, we need to get the type, etc...
         /// </summary>

Tests/test_array.py

@@ -279,4 +279,90 @@ def test_tuple_indexer(self):
         array1[0,0] = 5
         self.assertEqual(array1[0,0], array1[(0,0)])
 
+    def test_equality(self):
+        a = System.Array.CreateInstance(int, 5)
+        a2 = System.Array.CreateInstance(int, 5) # same as a
+        b = System.Array.CreateInstance(int, 5, 6) # different rank
+        c = System.Array.CreateInstance(int, 6) # different length
+        d = System.Array.CreateInstance(int, (5,), (1,)) # different base
+        e = System.Array.CreateInstance(System.Int32, 5) # different element type
+        l = [0] * 5 # different type
+
+        self.assertTrue(a == a2)
+        self.assertTrue(a2 == a)
+        self.assertFalse(a != a2)
+        self.assertFalse(a2 != a)
+
+        self.assertFalse(a == b)
+        self.assertFalse(b == a)
+        self.assertTrue(a != b)
+        self.assertTrue(b != a)
+
+        self.assertFalse(a == c)
+        self.assertFalse(c == a)
+        self.assertTrue(a != c)
+        self.assertTrue(c != a)
+
+        self.assertFalse(a == d)
+        self.assertFalse(d == a)
+        self.assertTrue(a != d)
+        self.assertTrue(d != a)
+
+        self.assertFalse(a == e)
+        self.assertFalse(e == a)
+        self.assertTrue(a != e)
+        self.assertTrue(e != a)
+
+        self.assertFalse(a == l)
+        self.assertFalse(l == a)
+        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__)