From 4333a9a8d6d9b98e0923e09e06deb41ee5bcd5b7 Mon Sep 17 00:00:00 2001 From: Lenny Maiorani Date: Wed, 23 Dec 2020 11:35:01 -0700 Subject: [PATCH] AK: Find a value in any container offering iterators Problem: - `find` is implemented inside of each container. This coupling requires that each container needs to individually provide `find`. Solution: - Decouple the `find` functionality from the container. This allows provides a `find` algorithm which can work with all containers. Containers can still provide their own `find` in the case where it can be optimized. - This also allows for searching sub-ranges of a container rather than the entire container as some of the container-specific member functions enforced. Note: - @davidstone's talk from 2015 C++Now conference entitled "Functions Want to be Free" encourages this style: (https://www.youtube.com/watch?v=_lVlC0xzXDc), but it does come at the cost of composability. - A logical follow-on to this is to provide a mechanism to use a short-hand function which automatically searches the entire container. This could automatically use the container-provided version if available so that functions which provide their own optimized version get the benefit. --- AK/Find.h | 57 +++++++++++++++++++++++++++++++ AK/Tests/CMakeLists.txt | 1 + AK/Tests/TestFind.cpp | 76 +++++++++++++++++++++++++++++++++++++++++ AK/Traits.h | 2 +- 4 files changed, 135 insertions(+), 1 deletion(-) create mode 100644 AK/Find.h create mode 100644 AK/Tests/TestFind.cpp diff --git a/AK/Find.h b/AK/Find.h new file mode 100644 index 00000000000..7832f877bd5 --- /dev/null +++ b/AK/Find.h @@ -0,0 +1,57 @@ +/* + * Copyright (c) 2021, the SerenityOS developers. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#pragma once + +#include +#include + +namespace AK { + +template +constexpr TIterator find_if(TIterator first, TIterator last, TUnaryPredicate&& pred) +{ + for (; first != last; ++first) { + if (pred(*first)) { + return first; + } + } + return last; +} + +template +constexpr TIterator find(TIterator first, TIterator last, const T& value) +{ + return find_if(first, last, [&](const auto& v) { return Traits::equals(value, v); }); +} + +template +constexpr size_t find_index(TIterator first, TIterator last, const T& value) +{ + return find_if(first, last, [&](const auto& v) { return Traits::equals(value, v); }).index(); +} + +} diff --git a/AK/Tests/CMakeLists.txt b/AK/Tests/CMakeLists.txt index 02ea1e5ac16..002b30092eb 100644 --- a/AK/Tests/CMakeLists.txt +++ b/AK/Tests/CMakeLists.txt @@ -12,6 +12,7 @@ set(AK_TEST_SOURCES TestCircularQueue.cpp TestDistinctNumeric.cpp TestEndian.cpp + TestFind.cpp TestFormat.cpp TestHashFunctions.cpp TestHashMap.cpp diff --git a/AK/Tests/TestFind.cpp b/AK/Tests/TestFind.cpp new file mode 100644 index 00000000000..190068911d5 --- /dev/null +++ b/AK/Tests/TestFind.cpp @@ -0,0 +1,76 @@ +/* + * Copyright (c) 2021, the SerenityOS developers. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include + +#include +#include +#include + +TEST_CASE(should_return_end_if_not_in_container) +{ + constexpr AK::Array a {}; + + static_assert(a.end() == AK::find(a.begin(), a.end(), 1)); + + EXPECT(a.end() == AK::find(a.begin(), a.end(), 1)); +} + +TEST_CASE(should_return_iterator_to_first_matching_value_in_container) +{ + static constexpr AK::Array a { 1, 2, 3, 4, 0, 6, 7, 8, 0, 0 }; + + constexpr auto expected = a.begin() + 4; + + static_assert(expected == AK::find(a.begin(), a.end(), 0)); + + EXPECT(expected == AK::find(a.begin(), a.end(), 0)); +} + +TEST_CASE(should_return_iterator_to_first_predicate_matching_value_in_container) +{ + static constexpr AK::Array a { 1, 2, 3, 4, 0, 6, 7, 8, 0, 0 }; + + constexpr auto expected = a.begin() + 4; + + static_assert(expected == AK::find_if(a.begin(), a.end(), [](auto v) { return v == 0; })); + + EXPECT(expected == AK::find_if(a.begin(), a.end(), [](auto v) { return v == 0; })); + + auto find_me = 8; + EXPECT(find_me == *AK::find_if(a.begin(), a.end(), [&](auto v) { return v == find_me; })); +} + +TEST_CASE(should_return_index_to_first_predicate_matching_value_in_container) +{ + static constexpr AK::Array a { 1, 2, 3, 4, 0, 6, 7, 8, 0, 0 }; + + static_assert(4 == AK::find_index(a.begin(), a.end(), 0)); + + EXPECT(4 == AK::find_index(a.begin(), a.end(), 0)); +} + +TEST_MAIN(Find) diff --git a/AK/Traits.h b/AK/Traits.h index 281c174af1c..ee53be14ec6 100644 --- a/AK/Traits.h +++ b/AK/Traits.h @@ -35,7 +35,7 @@ template struct GenericTraits { using PeekType = T; static constexpr bool is_trivial() { return false; } - static bool equals(const T& a, const T& b) { return a == b; } + static constexpr bool equals(const T& a, const T& b) { return a == b; } }; template