104 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++14, c++1710 11// Some basic examples of how elements_view might be used in the wild. This is a general12// collection of sample algorithms and functions that try to mock general usage of13// this view.14 15#include <algorithm>16#include <array>17#include <cassert>18#include <map>19#include <ranges>20#include <string_view>21#include <tuple>22#include <utility>23 24#include "test_iterators.h"25 26int main(int, char**) {27 using namespace std::string_view_literals;28 auto historicalFigures =29 std::map{std::pair{"Lovelace"sv, 1815}, {"Turing"sv, 1912}, {"Babbage"sv, 1791}, {"Hamilton"sv, 1936}};30 auto expectedYears = {1791, 1936, 1815, 1912};31 32 // views::elements<N>33 {34 auto names = historicalFigures | std::views::elements<0>;35 auto expectedNames = {"Babbage"sv, "Hamilton"sv, "Lovelace"sv, "Turing"sv};36 assert(std::ranges::equal(names, expectedNames));37 38 auto birth_years = historicalFigures | std::views::elements<1>;39 assert(std::ranges::equal(birth_years, expectedYears));40 }41 42 // views::keys43 {44 auto names = historicalFigures | std::views::keys;45 auto expectedNames = {"Babbage"sv, "Hamilton"sv, "Lovelace"sv, "Turing"sv};46 assert(std::ranges::equal(names, expectedNames));47 }48 49 // views::values50 {51 auto is_even = [](const auto x) { return x % 2 == 0; };52 assert(std::ranges::count_if(historicalFigures | std::views::values, is_even) == 2);53 }54 55 // array56 {57 std::array<int, 3> arrs[] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};58 auto ev = arrs | std::views::elements<2>;59 auto expected = {3, 6, 9};60 assert(std::ranges::equal(ev, expected));61 }62 63 // pair64 {65 std::pair<double, int> ps[] = {{1.0, 2}, {3.0, 4}, {5.0, 6}};66 auto ev = ps | std::views::elements<1>;67 auto expected = {2, 4, 6};68 assert(std::ranges::equal(ev, expected));69 }70 71 // tuple72 {73 std::tuple<short> tps[] = {{short{1}}, {short{2}}, {short{3}}};74 auto ev = tps | std::views::elements<0>;75 auto expected = {1, 2, 3};76 assert(std::ranges::equal(ev, expected));77 }78 79 // subrange80 {81 int is[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};82 using Iter = forward_iterator<int*>;83 using Sent = sentinel_wrapper<Iter>;84 using SubRange = std::ranges::subrange<Iter, Sent>;85 SubRange sr[] = {86 {Iter{is}, Sent{Iter{is + 1}}},87 {Iter{is + 2}, Sent{Iter{is + 5}}},88 {Iter{is + 6}, Sent{Iter{is + 8}}},89 };90 91 auto iters = sr | std::views::elements<0>;92 static_assert(std::is_same_v<Iter, std::ranges::range_reference_t<decltype(iters)>>);93 auto expectedIters = {is, is + 2, is + 6};94 assert(std::ranges::equal(iters | std::views::transform([](auto&& iter) { return base(iter); }), expectedIters));95 96 auto sentinels = sr | std::views::elements<1>;97 static_assert(std::is_same_v<Sent, std::ranges::range_reference_t<decltype(sentinels)>>);98 auto expectedSentinels = {is + 1, is + 5, is + 8};99 assert(std::ranges::equal(100 sentinels | std::views::transform([](auto&& st) { return base(base(st)); }), expectedSentinels));101 }102 return 0;103}104