Merge branch 'tgschultz-arraylist-remove'

std/array_list.zig

@@ -41,8 +41,8 @@ pub fn AlignedArrayList(comptime T: type, comptime A: u29) type {
             return self.items[0..self.len];
         }
 
-        pub fn at(self: Self, n: usize) T {
-            return self.toSliceConst()[n];
+        pub fn at(self: Self, i: usize) T {
+            return self.toSliceConst()[i];
         }
 
         /// Sets the value at index `i`, or returns `error.OutOfBounds` if
@@ -102,6 +102,26 @@ pub fn AlignedArrayList(comptime T: type, comptime A: u29) type {
             new_item_ptr.* = item;
         }
 
+        /// Removes the element at the specified index and returns it.
+        /// The empty slot is filled from the end of the list.
+        pub fn swapRemove(self: *Self, i: usize) T {
+            if (self.len - 1 == i) return self.pop();
+
+            const slice = self.toSlice();
+            const old_item = slice[i];
+            slice[i] = self.pop();
+            return old_item;
+        }
+
+        pub fn removeOrError(self: *Self, n: usize) !T {
+            if (n >= self.len) return error.OutOfBounds;
+            if (self.len - 1 == n) return self.pop();
+
+            var old_item = self.at(n);
+            try self.setOrError(n, self.pop());
+            return old_item;
+        }
+
         pub fn appendSlice(self: *Self, items: []align(A) const T) !void {
             try self.ensureCapacity(self.len + items.len);
             mem.copy(T, self.items[self.len..], items);
@@ -232,6 +252,33 @@ test "basic ArrayList test" {
     assert(list.pop() == 33);
 }
 
+test "std.ArrayList.swapRemove" {
+    var list = ArrayList(i32).init(debug.global_allocator);
+    defer list.deinit();
+
+    try list.append(1);
+    try list.append(2);
+    try list.append(3);
+    try list.append(4);
+    try list.append(5);
+    try list.append(6);
+    try list.append(7);
+
+    //remove from middle
+    assert(list.swapRemove(3) == 4);
+    assert(list.at(3) == 7);
+    assert(list.len == 6);
+
+    //remove from end
+    assert(list.swapRemove(5) == 6);
+    assert(list.len == 5);
+
+    //remove from front
+    assert(list.swapRemove(0) == 1);
+    assert(list.at(0) == 5);
+    assert(list.len == 4);
+}
+
 test "iterator ArrayList test" {
     var list = ArrayList(i32).init(debug.global_allocator);
     defer list.deinit();