base: add array

note: needed by math_opt

Author: Mizux

ortools/base/BUILD.bazel

@@ -97,6 +97,15 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "array",
+    srcs = ["array_internal.h"],
+    hdrs = ["array.h"],
+    deps = [
+        "@com_google_absl//absl/utility",
+    ],
+)
+
 cc_library(
     name = "basictypes",
     hdrs = ["basictypes.h"],

ortools/base/array.h

@@ -0,0 +1,51 @@
+// Copyright 2010-2025 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef OR_TOOLS_BASE_ARRAY_H_
+#define OR_TOOLS_BASE_ARRAY_H_
+
+//! @todo(corentinl) std::to_array available in C++20.
+
+#include <array>
+#include <cstddef>
+#include <type_traits>
+
+#include "absl/utility/utility.h"
+#include "ortools/base/array_internal.h"
+
+namespace gtl {
+
+/// A utility function to build `std::array` objects from built-in arrays
+/// without specifying their size.
+///
+/// Example:
+/// @code{.cpp}
+/// auto b = gtl::to_array<std::pair<int, int>>({
+///     {1, 2},
+///     {3, 4},
+/// });
+/// @endcode
+template <typename T, std::size_t N>
+constexpr std::array<std::remove_cv_t<T>, N> to_array(T (&ts)[N]) {
+  return internal_array::to_array_internal(ts, absl::make_index_sequence<N>{});
+}
+
+template <typename T, std::size_t N>
+constexpr std::array<std::remove_cv_t<T>, N> to_array(T (&&ts)[N]) {
+  return internal_array::to_array_internal(std::move(ts),
+                                           absl::make_index_sequence<N>{});
+}
+
+}  // namespace gtl
+
+#endif  // OR_TOOLS_BASE_ARRAY_H_

ortools/base/array_internal.h

@@ -0,0 +1,40 @@
+// Copyright 2010-2025 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef OR_TOOLS_BASE_ARRAY_INTERNAL_H_
+#define OR_TOOLS_BASE_ARRAY_INTERNAL_H_
+
+#include <array>
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+
+#include "absl/utility/utility.h"
+
+namespace gtl::internal_array {
+
+template <typename T, std::size_t N, std::size_t... Idx>
+constexpr std::array<std::remove_cv_t<T>, N> to_array_internal(
+    T (&ts)[N], absl::index_sequence<Idx...>) {
+  return {{ts[Idx]...}};
+}
+
+template <typename T, std::size_t N, std::size_t... Idx>
+constexpr std::array<std::remove_cv_t<T>, N> to_array_internal(
+    T (&&ts)[N], absl::index_sequence<Idx...>) {
+  return {{std::move(ts[Idx])...}};
+}
+
+}  // namespace gtl::internal_array
+
+#endif  // OR_TOOLS_BASE_ARRAY_INTERNAL_H_