utils: introduce ranges::to()

Sadly, std::ranges is missing an equivalent of boost::copy_range(), so
we introduce a replacement: ranges::to(). There is an existing proposal
to introduce something similar to the standard library:
std::ranges::to() (https://github.com/cplusplus/papers/issues/145). We
name our own version similarly, so if said proposal makes it in we can
just prepend std:: and be good.

Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20200529141407.158960-2-bdenes@scylladb.com>

utils/ranges.hh

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2020 ScyllaDB
+ */
+
+/*
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <ranges>
+
+namespace ranges {
+
+template <std::ranges::range Container, std::ranges::range Range>
+Container to(const Range& range) {
+    return Container(range.begin(), range.end());
+}
+
+}