93 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 drop_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 <ranges>16 17#include <vector>18#include <list>19#include <string>20 21#include <cassert>22#include "test_macros.h"23#include "test_iterators.h"24#include "types.h"25 26template<class T>27concept ValidDropView = requires { typename std::ranges::drop_view<T>; };28 29static_assert( ValidDropView<MoveOnlyView>);30static_assert(!ValidDropView<Range>);31 32static_assert(!std::ranges::enable_borrowed_range<std::ranges::drop_view<MoveOnlyView>>);33static_assert( std::ranges::enable_borrowed_range<std::ranges::drop_view<BorrowableView>>);34 35template<std::ranges::view View>36bool orderedFibonacci(View v, int n = 1) {37 if (v.size() < 3)38 return true;39 40 if (v[2] != v[0] + v[1])41 return false;42 43 return orderedFibonacci(std::ranges::drop_view(v.base(), n), n + 1);44}45 46template<std::ranges::view View>47std::ranges::view auto makeEven(View v) {48 return std::ranges::drop_view(v, v.size() % 2);49}50 51template<std::ranges::view View, class T>52int indexOf(View v, T element) {53 int index = 0;54 for (auto e : v) {55 if (e == element)56 return index;57 index++;58 }59 return -1;60}61 62template<std::ranges::view View, class T>63std::ranges::view auto removeBefore(View v, T element) {64 std::ranges::drop_view out(v, indexOf(v, element) + 1);65 return View(out.begin(), out.end());66}67 68template<>69constexpr bool std::ranges::enable_view<std::vector<int>> = true;70 71template<>72constexpr bool std::ranges::enable_view<std::list<int>> = true;73 74template<>75constexpr bool std::ranges::enable_view<std::string> = true;76 77int main(int, char**) {78 const std::vector vec = {1,1,2,3,5,8,13};79 assert(orderedFibonacci(std::ranges::drop_view(vec, 0)));80 const std::vector vec2 = {1,1,2,3,5,8,14};81 assert(!orderedFibonacci(std::ranges::drop_view(vec2, 0)));82 83 const std::list l = {1, 2, 3};84 auto el = makeEven(l);85 assert(el.size() == 2);86 assert(*el.begin() == 2);87 88 const std::string s = "Hello, World";89 assert(removeBefore(s, ' ') == "World");90 91 return 0;92}93