93 lines
2.5 KiB
C++
93 lines
2.5 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17
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// Some basic examples of how drop_view might be used in the wild. This is a general
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// collection of sample algorithms and functions that try to mock general usage of
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// this view.
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#include <ranges>
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#include <vector>
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#include <list>
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#include <string>
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#include <cassert>
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#include "test_macros.h"
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#include "test_iterators.h"
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#include "types.h"
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template<class T>
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concept ValidDropView = requires { typename std::ranges::drop_view<T>; };
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static_assert( ValidDropView<MoveOnlyView>);
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static_assert(!ValidDropView<Range>);
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static_assert(!std::ranges::enable_borrowed_range<std::ranges::drop_view<MoveOnlyView>>);
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static_assert( std::ranges::enable_borrowed_range<std::ranges::drop_view<BorrowableView>>);
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template<std::ranges::view View>
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bool orderedFibonacci(View v, int n = 1) {
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if (v.size() < 3)
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return true;
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if (v[2] != v[0] + v[1])
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return false;
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return orderedFibonacci(std::ranges::drop_view(v.base(), n), n + 1);
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}
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template<std::ranges::view View>
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std::ranges::view auto makeEven(View v) {
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return std::ranges::drop_view(v, v.size() % 2);
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}
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template<std::ranges::view View, class T>
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int indexOf(View v, T element) {
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int index = 0;
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for (auto e : v) {
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if (e == element)
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return index;
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index++;
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}
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return -1;
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}
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template<std::ranges::view View, class T>
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std::ranges::view auto removeBefore(View v, T element) {
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std::ranges::drop_view out(v, indexOf(v, element) + 1);
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return View(out.begin(), out.end());
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}
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template<>
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constexpr bool std::ranges::enable_view<std::vector<int>> = true;
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template<>
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constexpr bool std::ranges::enable_view<std::list<int>> = true;
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template<>
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constexpr bool std::ranges::enable_view<std::string> = true;
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int main(int, char**) {
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const std::vector vec = {1,1,2,3,5,8,13};
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assert(orderedFibonacci(std::ranges::drop_view(vec, 0)));
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const std::vector vec2 = {1,1,2,3,5,8,14};
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assert(!orderedFibonacci(std::ranges::drop_view(vec2, 0)));
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const std::list l = {1, 2, 3};
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auto el = makeEven(l);
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assert(el.size() == 2);
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assert(*el.begin() == 2);
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const std::string s = "Hello, World";
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assert(removeBefore(s, ' ') == "World");
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return 0;
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}
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