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/** @addtogroup Ranges
* @{
*/
/** @file algorithm.hh
*
* @brief Generic algorithms for working with ranges.
*
* This file provides various algorithms that work with ranges, including
* partitioning, sorting, comparison, iteration, finding, filling, folding,
* mapping, filtering and others. It's roughly equivalent to the C++ header
* `algorithm`, with many of the algorithms being just range-based versions
* of the iterator ones, but it also provides different custom algorithms.
*
* @copyright See COPYING.md in the project tree for further information.
*/
#ifndef OSTD_ALGORITHM_HH
#define OSTD_ALGORITHM_HH
#include <ostd/unit_test.hh>
#include <cmath>
#include <utility>
#include <functional>
#include <type_traits>
#include <algorithm>
#ifdef OSTD_BUILD_TESTS
#include <vector>
#endif
#include <ostd/range.hh>
#define OSTD_TEST_MODULE libostd_algorithm
namespace ostd {
/** @addtogroup Ranges
* @{
*/
/* partitioning */
/** @brief Partitions a range.
*
* Given a predicate `pred`, this rearranges the range so that items for
* which the predicate returns true are in the first part of the range.
*
* The range must meet the conditions of ostd::is_range_element_swappable.
*
* The predicate is applied `N` times and the swap is done at most `N` times.
*
* @returns The second part of the range.
*/
template<typename ForwardRange, typename Predicate>
inline ForwardRange partition(ForwardRange range, Predicate pred) {
static_assert(
is_range_element_swappable<ForwardRange>,
"The range element accessors must allow swapping"
);
auto ret = range;
for (; !range.empty(); range.pop_front()) {
if (pred(range.front())) {
using std::swap;
swap(range.front(), ret.front());
ret.pop_front();
}
}
return ret;
}
/** @brief A pipeable version of ostd::partition().
*
* The predicate is forwarded.
*/
template<typename Predicate>
inline auto partition(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return partition(obj, std::forward<Predicate>(pred));
};
}
/** @brief Checks if a range is partitioned as in ostd::partition().
*
* First, all elements matching `pred` are skipped and then if any of
* the elements following that match `pred`, false is returned. Otherwise,
* true is returned.
*
* The predicate is applied at most `N` times.
*/
template<typename InputRange, typename Predicate>
inline bool is_partitioned(InputRange range, Predicate pred) {
for (; !range.empty() && pred(range.front()); range.pop_front());
for (; !range.empty(); range.pop_front()) {
if (pred(range.front())) {
return false;
}
}
return true;
}
/** @brief A pipeable version of ostd::is_partitioned().
*
* The predicate is forwarded.
*/
template<typename Predicate>
inline auto is_partitioned(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return is_partitioned(obj, std::forward<Predicate>(pred));
};
}
#ifdef OSTD_BUILD_TESTS
OSTD_UNIT_TEST {
using ostd::test::fail_if;
using ostd::test::fail_if_not;
/* test with two vectors for pipeable and non-pipeable */
std::vector<int> v1 = { 5, 15, 10, 8, 36, 24 };
std::vector<int> v2 = v1;
auto try_test = [](auto &v, auto h) {
for (auto i: h) {
fail_if(i < 15);
}
for (auto i: iter(v).take(v.size() - h.size())) {
fail_if(i >= 15);
}
};
/* assume they're not partitioned */
fail_if(is_partitioned(iter(v1), [](int &i) { return i < 15; }));
fail_if(iter(v1) | is_partitioned([](int &i) { return i < 15; }));
fail_if(is_partitioned(iter(v2), [](int &i) { return i < 15; }));
fail_if(iter(v2) | is_partitioned([](int &i) { return i < 15; }));
/* partition now */
try_test(v1, partition(iter(v1), [](int &i) { return i < 15; }));
try_test(v2, iter(v2) | partition([](int &i) { return i < 15; }));
/* assume partitioned */
fail_if_not(is_partitioned(iter(v1), [](int &i) { return i < 15; }));
fail_if_not(iter(v1) | is_partitioned([](int &i) { return i < 15; }));
fail_if_not(is_partitioned(iter(v2), [](int &i) { return i < 15; }));
fail_if_not(iter(v2) | is_partitioned([](int &i) { return i < 15; }));
}
#endif
/* sorting */
namespace detail {
template<typename R, typename C>
inline void insort(R range, C &compare) {
range_size_t<R> rlen = range.size();
for (range_size_t<R> i = 1; i < rlen; ++i) {
range_size_t<R> j = i;
range_value_t<R> v{std::move(range[i])};
while (j > 0 && !compare(range[j - 1], v)) {
range[j] = std::move(range[j - 1]);
--j;
}
range[j] = std::move(v);
}
}
template<typename R, typename C>
inline void hs_sift_down(
R range, range_size_t<R> s, range_size_t<R> e, C &compare
) {
range_size_t<R> r = s;
while ((r * 2 + 1) <= e) {
range_size_t<R> ch = r * 2 + 1;
range_size_t<R> sw = r;
if (compare(range[sw], range[ch])) {
sw = ch;
}
if (((ch + 1) <= e) && compare(range[sw], range[ch + 1])) {
sw = ch + 1;
}
if (sw != r) {
using std::swap;
swap(range[r], range[sw]);
r = sw;
} else {
return;
}
}
}
template<typename R, typename C>
inline void heapsort(R range, C &compare) {
range_size_t<R> len = range.size();
range_size_t<R> st = (len - 2) / 2;
for (;;) {
detail::hs_sift_down(range, st, len - 1, compare);
if (st-- == 0) {
break;
}
}
range_size_t<R> e = len - 1;
while (e > 0) {
using std::swap;
swap(range[e], range[0]);
--e;
detail::hs_sift_down(range, 0, e, compare);
}
}
template<typename R, typename C>
inline void introloop(R range, C &compare, range_size_t<R> depth) {
using std::swap;
if (range.size() <= 10) {
detail::insort(range, compare);
return;
}
if (depth == 0) {
detail::heapsort(range, compare);
return;
}
swap(range[range.size() / 2], range.back());
range_size_t<R> pi = 0;
R pr = range;
pr.pop_back();
for (; !pr.empty(); pr.pop_front()) {
if (compare(pr.front(), range.back())) {
swap(pr.front(), range[pi++]);
}
}
swap(range[pi], range.back());
detail::introloop(range.slice(0, pi), compare, depth - 1);
detail::introloop(range.slice(pi + 1), compare, depth - 1);
}
template<typename R, typename C>
inline void introsort(R range, C &compare) {
detail::introloop(range, compare, static_cast<range_size_t<R>>(
2 * (std::log(range.size()) / std::log(2))
));
}
} /* namespace detail */
/** @brief Sorts a range given a comparison function.
*
* The range must be at least ostd::finite_random_access_range_tag. The
* comparison function takes two `ostd::range_reference_t<R>` and must
* return a boolean equivalent to `a < b` for ascending order.
*
* The items are swapped in the range, which means the range must also
* meet the conditions of ostd::is_range_element_swappable.
*
* The worst-case and average performance of this algorithm os `O(n log n)`.
* The best-case performance is `O(n)`. This happens when the range is small
* enough and already sorted (insertion sort is used for small ranges).
*
* The actual algorithm used is a hybrid algorithm between quicksort and
* heapsort (intosort) with insertion sort for small ranges.
*
* @see ostd::sort()
*/
template<typename FiniteRandomRange, typename Compare>
inline FiniteRandomRange sort_cmp(FiniteRandomRange range, Compare compare) {
static_assert(
is_range_element_swappable<FiniteRandomRange>,
"The range element accessors must allow swapping"
);
detail::introsort(range, compare);
return range;
}
/** @brief A pipeable version of ostd::sort_cmp().
*
* The comparison function is forwarded.
*/
template<typename Compare>
inline auto sort_cmp(Compare &&compare) {
return [compare = std::forward<Compare>(compare)](auto &obj) mutable {
return sort_cmp(obj, std::forward<Compare>(compare));
};
}
/** @brief Like ostd::sort_cmp() using `std::less<ostd::range_value_t<R>>{}`. */
template<typename FiniteRandomRange>
inline FiniteRandomRange sort(FiniteRandomRange range) {
static_assert(
is_range_element_swappable<FiniteRandomRange>,
"The range element accessors must allow swapping"
);
return sort_cmp(range, std::less<range_value_t<FiniteRandomRange>>{});
}
/** @brief A pipeable version of ostd::sort(). */
inline auto sort() {
return [](auto &obj) { return sort(obj); };
}
/* min/max(_element) */
/** @brief Finds the smallest element in the range.
*
* It works like std::min_element(). The range must be at least
* ostd::forward_range_tag. The `<` operator is used for comparisons.
*
* @see ostd::min_element_cmp(), ostd::max_element()
*/
template<typename ForwardRange>
inline ForwardRange min_element(ForwardRange range) {
ForwardRange r = range;
for (; !range.empty(); range.pop_front()) {
if (std::min(r.front(), range.front()) == range.front()) {
r = range;
}
}
return r;
}
/** @brief Finds the smallest element in the range.
*
* It works like std::min_element. The range must be at least
* ostd::forward_range_tag. The `compare` function is used for comparisons.
*
* @see ostd::min_element(), ostd::max_element_cmp()
*/
template<typename ForwardRange, typename Compare>
inline ForwardRange min_element_cmp(ForwardRange range, Compare compare) {
ForwardRange r = range;
for (; !range.empty(); range.pop_front()) {
if (std::min(r.front(), range.front(), compare) == range.front()) {
r = range;
}
}
return r;
}
/** @brief A pipeable version of ostd::min_element(). */
inline auto min_element() {
return [](auto &obj) {
return min_element(obj);
};
}
/** @brief A pipeable version of ostd::min_element_cmp().
*
* The comparison function is forwarded.
*/
template<typename Compare>
inline auto min_element_cmp(Compare &&compare) {
return [compare = std::forward<Compare>(compare)](auto &obj) mutable {
return min_element_cmp(obj, std::forward<Compare>(compare));
};
}
/** @brief Finds the largest element in the range.
*
* It works like std::max_element(). The range must be at least
* ostd::forward_range_tag. The `<` operator is used for comparisons.
*
* @see ostd::max_element_cmp(), ostd::min_element()
*/
template<typename ForwardRange>
inline ForwardRange max_element(ForwardRange range) {
ForwardRange r = range;
for (; !range.empty(); range.pop_front()) {
if (std::max(r.front(), range.front()) == range.front()) {
r = range;
}
}
return r;
}
/** @brief Finds the largest element in the range.
*
* It works like std::max_element. The range must be at least
* ostd::forward_range_tag. The `compare` function is used for comparisons.
*
* @see ostd::max_element(), ostd::min_element_cmp()
*/
template<typename ForwardRange, typename Compare>
inline ForwardRange max_element_cmp(ForwardRange range, Compare compare) {
ForwardRange r = range;
for (; !range.empty(); range.pop_front()) {
if (std::max(r.front(), range.front(), compare) == range.front()) {
r = range;
}
}
return r;
}
/** @brief A pipeable version of ostd::max_element(). */
inline auto max_element() {
return [](auto &obj) {
return max_element(obj);
};
}
/** @brief A pipeable version of ostd::max_element_cmp().
*
* The comparison function is forwarded.
*/
template<typename Compare>
inline auto max_element_cmp(Compare &&compare) {
return [compare = std::forward<Compare>(compare)](auto &obj) mutable {
return max_element_cmp(obj, std::forward<Compare>(compare));
};
}
/* lexicographical compare */
/** @brief Like std::lexicographical_compare(), but for ranges.
*
* This version uses the `<` operator for comparisons. This algorithm
* is not multi-pass, so an ostd::input_range_tag is perfectly fine here.
*
* @see ostd::lexicographical_compare_cmp()
*/
template<typename InputRange1, typename InputRange2>
inline bool lexicographical_compare(InputRange1 range1, InputRange2 range2) {
while (!range1.empty() && !range2.empty()) {
if (range1.front() < range2.front()) {
return true;
}
if (range2.front() < range1.front()) {
return false;
}
range1.pop_front();
range2.pop_front();
}
return (range1.empty() && !range2.empty());
}
/** @brief A pipeable version of ostd::lexicographical_compare().
*
* The range is forwarded.
*/
template<typename InputRange>
inline auto lexicographical_compare(InputRange &&range) {
return [range = std::forward<InputRange>(range)](auto &obj) mutable {
return lexicographical_compare(obj, std::forward<InputRange>(range));
};
}
/** @brief Like std::lexicographical_compare(), but for ranges.
*
* This version uses the `compare` function for comparisons. This algorithm
* is not multi-pass, so an ostd::input_range_tag is perfectly fine here.
*
* @see ostd::lexicographical_compare()
*/
template<typename InputRange1, typename InputRange2, typename Compare>
inline bool lexicographical_compare_cmp(
InputRange1 range1, InputRange2 range2, Compare compare
) {
while (!range1.empty() && !range2.empty()) {
if (compare(range1.front(), range2.front())) {
return true;
}
if (compare(range2.front(), range1.front())) {
return false;
}
range1.pop_front();
range2.pop_front();
}
return (range1.empty() && !range2.empty());
}
/** @brief A pipeable version of ostd::lexicographical_compare_cmp().
*
* The range and comparison function are forwarded.
*/
template<typename InputRange, typename Compare>
inline auto lexicographical_compare_cmp(InputRange &&range, Compare &&compare) {
return [
range = std::forward<InputRange>(range),
compare = std::forward<Compare>(compare)
](auto &obj) mutable {
return lexicographical_compare_cmp(
obj, std::forward<InputRange>(range), std::forward<Compare>(compare)
);
};
}
/* algos that don't change the range */
/** @brief Executes `func` on each element of `range`.
*
* The `func` is called like `func(range.front())`. The algorithm is
* not multi-pass, so an ostd::input_range_tag is perfectly fine.
*
* @returns The `func` by move.
*/
template<typename InputRange, typename UnaryFunction>
inline UnaryFunction for_each(InputRange range, UnaryFunction func) {
for (; !range.empty(); range.pop_front()) {
func(range.front());
}
return func;
}
/** @brief A pipeable version of ostd::for_each().
*
* The function is forwarded.
*/
template<typename UnaryFunction>
inline auto for_each(UnaryFunction &&func) {
return [func = std::forward<UnaryFunction>(func)](auto &obj) mutable {
return for_each(obj, std::forward<UnaryFunction>(func));
};
}
/** @brief Checks if every element of `range` matches `pred`.
*
* The `pred` has to return true when called like `pred(range.front())`.
* If it doesn't, `false` is returned.
*
* The predicate is called at most `N` times, where `N` is the range length.
* The range is an ostd::input_range_tag or better.
*
* @see ostd::any_of(), ostd::none_of()
*/
template<typename InputRange, typename Predicate>
inline bool all_of(InputRange range, Predicate pred) {
for (; !range.empty(); range.pop_front()) {
if (!pred(range.front())) {
return false;
}
}
return true;
}
/** @brief A pipeable version of ostd::all_of().
*
* The function is forwarded.
*/
template<typename Predicate>
inline auto all_of(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return all_of(obj, std::forward<Predicate>(pred));
};
}
/** @brief Checks if any element of `range` matches `pred`.
*
* As soon as `pred` returns true when called like `pred(range.front())`,
* this returns true. Otherwise it returns false.
*
* The predicate is called at most `N` times, where `N` is the range length.
* The range is an ostd::input_range_tag or better.
*
* @see ostd::all_of(), ostd::none_of()
*/
template<typename InputRange, typename Predicate>
inline bool any_of(InputRange range, Predicate pred) {
for (; !range.empty(); range.pop_front())
if (pred(range.front())) return true;
return false;
}
/** @brief A pipeable version of ostd::any_of().
*
* The function is forwarded.
*/
template<typename Predicate>
inline auto any_of(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return any_of(obj, std::forward<Predicate>(pred));
};
}
/** @brief Checks if no element of `range` matches `pred`.
*
* As soon as `pred` returns true when called like `pred(range.front())`,
* this returns false. Otherwise it returns true.
*
* The predicate is called at most `N` times, where `N` is the range length.
* The range is an ostd::input_range_tag or better.
*
* @see ostd::all_of(), ostd::any_of()
*/
template<typename InputRange, typename Predicate>
inline bool none_of(InputRange range, Predicate pred) {
for (; !range.empty(); range.pop_front())
if (pred(range.front())) return false;
return true;
}
/** @brief A pipeable version of ostd::none_of().
*
* The function is forwarded.
*/
template<typename Predicate>
inline auto none_of(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return none_of(obj, std::forward<Predicate>(pred));
};
}
/** @brief Finds `v` in `range`.
*
* Iterates the range and as soon as `range.front()` is equal to `v`,
* returns `range`. The `range` is at least ostd::input_range_tag.
*
* @see ostd::find_last(), ostd::find_if(), ostd::find_if_not(),
* ostd::find_one_of()
*/
template<typename InputRange, typename Value>
inline InputRange find(InputRange range, Value const &v) {
for (; !range.empty(); range.pop_front()) {
if (range.front() == v) {
break;
}
}
return range;
}
/** @brief A pipeable version of ostd::find().
*
* The `v` is forwarded.
*/
template<typename Value>
inline auto find(Value &&v) {
return [v = std::forward<Value>(v)](auto &obj) mutable {
return find(obj, std::forward<Value>(v));
};
}
/** @brief Finds the last occurence of `v` in `range`.
*
* Keeps attempting ostd::find() from the point of previous ostd::find()
* until no next matching element is found. As this algorithm has to save
* the previous result of ostd::find() in case nothing is found next, this
* algortihm requires `range` to be at least ostd::forward_range_tag.
*
* @see ostd::find(), ostd::find_if(), ostd::find_if_not(),
* ostd::find_one_of()
*/
template<typename ForwardRange, typename Value>
inline ForwardRange find_last(ForwardRange range, Value const &v) {
range = find(range, v);
if (!range.empty()) {
for (;;) {
auto prev = range;
prev.pop_front();
auto r = find(prev, v);
if (r.empty()) {
break;
}
range = r;
}
}
return range;
}
/** @brief A pipeable version of ostd::find_last().
*
* The `v` is forwarded.
*/
template<typename Value>
inline auto find_last(Value &&v) {
return [v = std::forward<Value>(v)](auto &obj) mutable {
return find_last(obj, std::forward<Value>(v));
};
}
/** @brief Finds an element matching `pred` in `range`.
*
* Iterates the range and as soon as `pred(range.front())` is true,
* returns `range`. The `range` is at least ostd::input_range_tag.
*
* @see ostd::find(), ostd::find_last(), ostd::find_if_not(),
* ostd::find_one_of()
*/
template<typename InputRange, typename Predicate>
inline InputRange find_if(InputRange range, Predicate pred) {
for (; !range.empty(); range.pop_front()) {
if (pred(range.front())) {
break;
}
}
return range;
}
/** @brief A pipeable version of ostd::find_if().
*
* The `pred` is forwarded.
*/
template<typename Predicate>
inline auto find_if(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return find_if(obj, std::forward<Predicate>(pred));
};
}
/** @brief Finds an element not matching `pred` in `range`.
*
* Iterates the range and as soon as `!pred(range.front())` is true,
* returns `range`. The `range` is at least ostd::input_range_tag.
*
* @see ostd::find(), ostd::find_last(), ostd::find_if(), ostd::find_one_of()
*/
template<typename InputRange, typename Predicate>
inline InputRange find_if_not(InputRange range, Predicate pred) {
for (; !range.empty(); range.pop_front()) {
if (!pred(range.front())) {
break;
}
}
return range;
}
/** @brief A pipeable version of ostd::find_if_not().
*
* The `pred` is forwarded.
*/
template<typename Predicate>
inline auto find_if_not(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return find_if_not(obj, std::forward<Predicate>(pred));
};
}
/** @brief Finds the first element matching any element in `values`.
*
* The `compare` function is used to compare the values. The `range`
* is iterated and each item is compared with each item in `values`
* and once a match is found, `range` is returned.
*
* The `range` has to be at least ostd::input_range_tag as it's
* iterated only once, `values` has to be ostd::forward_range_tag or
* better.
*
* The time complexity is up to `N * M` where `N` is the length of
* `range` and `M` is the length of `values`.
*
* Use ostd::find_one_of() if you want to use the `==` operator
* instead of calling `compare`.
*
* @see ostd::find(), ostd::find_last(), ostd::find_if(), ostd::find_if_not(),
* ostd::find_one_of()
*/
template<typename InputRange, typename ForwardRange, typename Compare>
inline InputRange find_one_of_cmp(
InputRange range, ForwardRange values, Compare compare
) {
for (; !range.empty(); range.pop_front()) {
for (auto rv = values; !rv.empty(); rv.pop_front()) {
if (compare(range.front(), rv.front())) {
return range;
}
}
}
return range;
}
/** @brief A pipeable version of ostd::find_one_of_cmp().
*
* The `values` and `compare` are forwarded.
*/
template<typename ForwardRange, typename Compare>
inline auto find_one_of_cmp(ForwardRange &&values, Compare &&compare) {
return [
values = std::forward<ForwardRange>(values),
compare = std::forward<Compare>(compare)
](auto &obj) mutable {
return find_one_of_cmp(
obj, std::forward<ForwardRange>(values),
std::forward<Compare>(compare)
);
};
}
/** @brief Finds the first element matching any element in `values`.
*
* The `==` operator is used to compare the values. The `range`
* is iterated and each item is compared with each item in `values`
* and once a match is found, `range` is returned.
*
* The `range` has to be at least ostd::input_range_tag as it's
* iterated only once, `values` has to be ostd::forward_range_tag or
* better.
*
* The time complexity is up to `N * M` where `N` is the length of
* `range` and `M` is the length of `values`.
*
* Use ostd::find_one_of_cmp() if you want to use a comparison
* function instead of the `==` operator.
*
* @see ostd::find(), ostd::find_last(), ostd::find_if(), ostd::find_if_not(),
* ostd::find_one_of_cmp()
*/
template<typename InputRange, typename ForwardRange>
inline InputRange find_one_of(InputRange range, ForwardRange values) {
for (; !range.empty(); range.pop_front()) {
for (auto rv = values; !rv.empty(); rv.pop_front()) {
if (range.front() == rv.front()) {
return range;
}
}
}
return range;
}
/** @brief A pipeable version of ostd::find_one_of().
*
* The `values` range is forwarded.
*/
template<typename ForwardRange>
inline auto find_one_of(ForwardRange &&values) {
return [values = std::forward<ForwardRange>(values)](auto &obj) mutable {
return find_one_of(obj, std::forward<ForwardRange>(values));
};
}
/** @brief Counts the number of occurences of `v` in `range`.
*
* Iterates the range and each time `v` is encountered (using the `==`
* operator) a counter is incremented. This counter is then returned.
*
* The `range` is at least ostd::input_range_tag.
*
* @see ostd::count_if(), ostd::count_if_not()
*/
template<typename InputRange, typename Value>
inline range_size_t<InputRange> count(InputRange range, Value const &v) {
range_size_t<InputRange> ret = 0;
for (; !range.empty(); range.pop_front()) {
if (range.front() == v) {
++ret;
}
}
return ret;
}
/** @brief A pipeable version of ostd::count().
*
* The `v` is forwarded.
*/
template<typename Value>
inline auto count(Value &&v) {
return [v = std::forward<Value>(v)](auto &obj) mutable {
return count(obj, std::forward<Value>(v));
};
}
/** @brief Counts the number of elements matching `pred` in `range.
*
* Iterates the range and each time `pred(range.front())` returns true,
* a counter is incremented. This counter is then returned.
*
* The `range` is at least ostd::input_range_tag.
*
* @see ostd::count(), ostd::count_if_not()
*/
template<typename InputRange, typename Predicate>
inline range_size_t<InputRange> count_if(InputRange range, Predicate pred) {
range_size_t<InputRange> ret = 0;
for (; !range.empty(); range.pop_front()) {
if (pred(range.front())) {
++ret;
}
}
return ret;
}
/** @brief A pipeable version of ostd::count_if().
*
* The `pred` is forwarded.
*/
template<typename Predicate>
inline auto count_if(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return count_if(obj, std::forward<Predicate>(pred));
};
}
/** @brief Counts the number of elements not matching `pred` in `range.
*
* Iterates the range and each time `!pred(range.front())` returns true,
* a counter is incremented. This counter is then returned.
*
* The `range` is at least ostd::input_range_tag.
*
* @see ostd::count(), ostd::count_if()
*/
template<typename InputRange, typename Predicate>
inline range_size_t<InputRange> count_if_not(InputRange range, Predicate pred) {
range_size_t<InputRange> ret = 0;
for (; !range.empty(); range.pop_front()) {
if (!pred(range.front())) {
++ret;
}
}
return ret;
}
/** @brief A pipeable version of ostd::count_if_not().
*
* The `pred` is forwarded.
*/
template<typename Predicate>
inline auto count_if_not(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return count_if_not(obj, std::forward<Predicate>(pred));
};
}
/** @brief Checks if two ranges have equal contents.
*
* Both ranges are at least ostd::input_range_tag. If one range becomes
* empty before the other does, false is returned. If the expression
* `!(range1.front() == range2.front())` is true in any iteration,
* false is also returned. Otherwise true is returned.
*/
template<typename InputRange>
inline bool equal(InputRange range1, InputRange range2) {
for (; !range1.empty(); range1.pop_front()) {
if (range2.empty() || !(range1.front() == range2.front())) {
return false;
}
range2.pop_front();
}
return range2.empty();
}
/** @brief A pipeable version of ostd::equal().
*
* The `range` is forwarded as the second range.
*/
template<typename InputRange>
inline auto equal(InputRange &&range) {
return [range = std::forward<InputRange>(range)](auto &obj) mutable {
return equal(obj, std::forward<InputRange>(range));
};
}
/* algos that modify ranges or work with output ranges */
/** @brief Copies all elements from `irange` to `orange`.
*
* The `irange` is at least ostd::input_range_tag. The `orange` is
* an output range. The ostd::range_put_all() function is used to
* perform the copy. it respects ADL and therefore any per-type
* overloads of ostd::range_put_all.
*
* @see ostd::copy_if(), ostd::copy_if_not()
*/
template<typename InputRange, typename OutputRange>
inline OutputRange copy(InputRange irange, OutputRange orange) {
range_put_all(orange, irange);
return orange;
}
/** @brief Copies elements of `irange` matching `pred` into `orange`.
*
* The `irange` (at least ostd::input_range_tag) is iterated and if
* the expression `pred(irange.front())` is true, the element is
* inserted (like `orange.put(irange.front())`).
*
* @see ostd::copy(), ostd::copy_if_not()
*/
template<typename InputRange, typename OutputRange, typename Predicate>
inline OutputRange copy_if(
InputRange irange, OutputRange orange, Predicate pred
) {
for (; !irange.empty(); irange.pop_front()) {
if (pred(irange.front())) {
orange.put(irange.front());
}
}
return orange;
}
/** @brief Copies elements of `irange` not matching `pred` into `orange`.
*
* The `irange` (at least ostd::input_range_tag) is iterated and if
* the expression `!pred(irange.front())` is true, the element is
* inserted (like `orange.put(irange.front())`).
*
* @see ostd::copy(), ostd::copy_if()
*/
template<typename InputRange, typename OutputRange, typename Predicate>
inline OutputRange copy_if_not(
InputRange irange, OutputRange orange, Predicate pred
) {
for (; !irange.empty(); irange.pop_front()) {
if (!pred(irange.front())) {
orange.put(irange.front());
}
}
return orange;
}
/** @brief Reverses the order of the given range in-place.
*
* The range must be at least ostd::bidirectional_range_tag. The range
* must also meet the conditions of ostd::is_range_element_swappable.
*
* Equivalent to the following:
*
* ~~~{.cc}
* while (!range.empty()) {
* using std::swap;
* swap(range.front(), range.back());
* range.pop_front();
* range.pop_back();
* }
* ~~~
*
* @see ostd::reverse_copy()
*/
template<typename BidirRange>
inline void reverse(BidirRange range) {
static_assert(
is_range_element_swappable<BidirRange>,
"The range element accessors must allow swapping"
);
while (!range.empty()) {
using std::swap;
swap(range.front(), range.back());
range.pop_front();
range.pop_back();
}
}
/** @brief Reverses the order of the given range into `orange`.
*
* Iterates `irange` backwards, putting each item into `orange`. The
* `irange` has to be at least ostd::bidirectional_range_tag.
*
* Equivalent to the following:
*
* ~~~{.cc}
* while (!irange.empty()) {
* orange.put(irange.back());
* irange.pop_back();
* }
*
* return orange;
* ~~~
*
* @see ostd::reverse()
*/
template<typename BidirRange, typename OutputRange>
inline OutputRange reverse_copy(BidirRange irange, OutputRange orange) {
for (; !irange.empty(); irange.pop_back()) {
orange.put(irange.back());
}
return orange;
}
/** @brief Fills the given input range with `v`.
*
* Iterates over `range` and assigns `v` to each element. The elements
* must therefore be actual lvalue references so they can be assigned to.
*
* @see ostd::generate(), ostd::iota()
*/
template<typename InputRange, typename Value>
inline void fill(InputRange range, Value const &v) {
for (; !range.empty(); range.pop_front()) {
range.front() = v;
}
}
/** @brief Fills the given input range with calls to `gen`.
*
* Iterates over `range` and assigns `gen()` to each element. The elements
* must therefore be actual lvalue references so they can be assigned to.
*
* @see ostd::fill(), ostd::iota()
*/
template<typename InputRange, typename UnaryFunction>
inline void generate(InputRange range, UnaryFunction gen) {
for (; !range.empty(); range.pop_front()) {
range.front() = gen();
}
}
/** @brief Swaps the contents of two input ranges.
*
* Testing ostd::is_range_element_swappable_with must be true with the given
* ranges. The ranges must be at least ostd::input_range_tag. The swapping
* stops as soon as any of the ranges becomes empty.
*
* @returns The `range1` and `range2` in a pair after swapping is done.
*/
template<typename InputRange1, typename InputRange2>
inline std::pair<InputRange1, InputRange2> swap_ranges(
InputRange1 range1, InputRange2 range2
) {
static_assert(
is_range_element_swappable_with<InputRange1, InputRange2>,
"The range element accessors must allow swapping"
);
while (!range1.empty() && !range2.empty()) {
using std::swap;
swap(range1.front(), range2.front());
range1.pop_front();
range2.pop_front();
}
return std::make_pair(range1, range2);
}
/** @brief Fills the given input range with `value++`.
*
* Iterates over `range` and assigns `value++` to each element. The elements
* must therefore be actual lvalue references so they can be assigned to.
*
* @see ostd::fill(), ostd::generate()
*/
template<typename InputRange, typename Value>
inline void iota(InputRange range, Value value) {
for (; !range.empty(); range.pop_front()) {
range.front() = value++;
}
}
/** @brief Left-folds the `range` into `init`.
*
* The `init` is an initial value. The `range` is iterated and each
* element is added to `init` using the `+` operator. Once that is
* done, `init` is returned.
*
* The `range` must be at least ostd::input_range_tag.
*
* A function-based version as well as right-folds are provided as well.
*
* @see ostd::foldl_f(), ostd::foldr()
*/
template<typename InputRange, typename Value>
inline Value foldl(InputRange range, Value init) {
for (; !range.empty(); range.pop_front()) {
init = init + range.front();
}
return init;
}
/** @brief Left-folds the `range` into `init`.
*
* The `init` is an initial value. The `range` is iterated and `init`
* is assigned as `init = func(init, range.front())`. Once that is
* done, `init` is returned.
*
* The `range` must be at least ostd::input_range_tag.
*
* A `+` operator-based version as well as right-folds are provided as well.
*
* @see ostd::foldl(), ostd::foldr_f()
*/
template<typename InputRange, typename Value, typename BinaryFunction>
inline Value foldl_f(InputRange range, Value init, BinaryFunction func) {
for (; !range.empty(); range.pop_front()) {
init = func(init, range.front());
}
return init;
}
/** @brief A pipeable version of ostd::foldl().
*
* The `init` is forwarded.
*/
template<typename Value>
inline auto foldl(Value &&init) {
return [init = std::forward<Value>(init)](auto &obj) mutable {
return foldl(obj, std::forward<Value>(init));
};
}
/** @brief A pipeable version of ostd::foldl_f().
*
* The `init` and `func` are forwarded.
*/
template<typename Value, typename BinaryFunction>
inline auto foldl_f(Value &&init, BinaryFunction &&func) {
return [
init = std::forward<Value>(init),
func = std::forward<BinaryFunction>(func)
](auto &obj) mutable {
return foldl_f(
obj, std::forward<Value>(init), std::forward<BinaryFunction>(func)
);
};
}
/** @brief Right-folds the `range` into `init`.
*
* The `init` is an initial value. The `range` is iterated backwards
* and each element is added to `init` using the `+` operator. Once
* that is done, `init` is returned.
*
* The `range` must be at least ostd::bidirectional_range_tag.
*
* A function-based version as well as left-folds are provided as well.
*
* @see ostd::foldr_f(), ostd::foldl()
*/
template<typename InputRange, typename Value>
inline Value foldr(InputRange range, Value init) {
for (; !range.empty(); range.pop_back()) {
init = init + range.back();
}
return init;
}
/** @brief Right-folds the `range` into `init`.
*
* The `init` is an initial value. The `range` is iterated backwards
* and `init` is assigned as `init = func(init, range.back())`. Once
* that is done, `init` is returned.
*
* The `range` must be at least ostd::bidirectional_range_tag.
*
* A `+` operator-based version as well as left-folds are provided as well.
*
* @see ostd::foldr(), ostd::foldl_f()
*/
template<typename InputRange, typename Value, typename BinaryFunction>
inline Value foldr_f(InputRange range, Value init, BinaryFunction func) {
for (; !range.empty(); range.pop_back()) {
init = func(init, range.back());
}
return init;
}
/** @brief A pipeable version of ostd::foldr().
*
* The `init` is forwarded.
*/
template<typename Value>
inline auto foldr(Value &&init) {
return [init = std::forward<Value>(init)](auto &obj) mutable {
return foldr(obj, std::forward<Value>(init));
};
}
/** @brief A pipeable version of ostd::foldr_f().
*
* The `init` and `func` are forwarded.
*/
template<typename Value, typename BinaryFunction>
inline auto foldr_f(Value &&init, BinaryFunction &&func) {
return [
init = std::forward<Value>(init),
func = std::forward<BinaryFunction>(func)
](auto &obj) mutable {
return foldr_f(
obj, std::forward<Value>(init), std::forward<BinaryFunction>(func)
);
};
}
namespace detail {
template<typename T, typename F, typename R>
struct map_range: input_range<map_range<T, F, R>> {
using range_category = std::common_type_t<
range_category_t<T>, finite_random_access_range_tag
>;
using value_type = std::remove_reference_t<R>;
using reference = R;
using size_type = range_size_t<T>;
private:
T p_range;
std::decay_t<F> p_func;
public:
map_range() = delete;
template<typename FF>
map_range(T const &range, FF &&func):
p_range(range), p_func(std::forward<FF>(func)) {}
bool empty() const { return p_range.empty(); }
size_type size() const { return p_range.size(); }
void pop_front() { p_range.pop_front(); }
void pop_back() { p_range.pop_back(); }
R front() const { return p_func(p_range.front()); }
R back() const { return p_func(p_range.back()); }
R operator[](size_type idx) const {
return p_func(p_range[idx]);
}
map_range slice(size_type start, size_type end) const {
return map_range(p_range.slice(start, end), p_func);
}
map_range slice(size_type start) const {
return slice(start, size());
}
};
template<typename R, typename F>
using MapReturnType = decltype(
std::declval<F>()(std::declval<range_reference_t<R>>())
);
} /* namespace detail */
/** @brief Gets a wrapper range that maps each item by `func`.
*
* The resulting range is at most ostd::finite_random_access_range_tag.
* There are no restrictions on the input range. The resulting range is
* not mutable, it's purely input-type.
*
* The `reference` member type of the range is `R` where `R` is the return
* value of `func`. The `value_type` is `std::remove_reference_t<R>`. The
* size type is preserved.
*
* On each access of a range item (front, back, indexing), the `func` is
* called with the actual wrapped range's item and the result is returned.
*
* An example:
*
* ~~~{.cc}
* auto r = ostd::map(ostd::range(5), [](auto v) { return v + 5; });
* for (auto i: r) {
* ostd::writeln(i); // 5, 6, 7, 8, 9
* }
* ~~~
*
* Because the range is lazy, a new value is computed on each access, but
* the wrapper range also needs no memory of its own.
*
* @see ostd::filter()
*/
template<typename InputRange, typename UnaryFunction>
inline auto map(InputRange range, UnaryFunction func) {
return detail::map_range<
InputRange, UnaryFunction,
detail::MapReturnType<InputRange, UnaryFunction>
>(range, std::move(func));
}
/** @brief A pipeable version of ostd::map().
*
* The `func` is forwarded.
*/
template<typename UnaryFunction>
inline auto map(UnaryFunction &&func) {
return [func = std::forward<UnaryFunction>(func)](auto &obj) mutable {
return map(obj, std::forward<UnaryFunction>(func));
};
}
namespace detail {
template<typename T, typename F>
struct filter_range: input_range<filter_range<T, F>> {
using range_category = std::common_type_t<
range_category_t<T>, forward_range_tag
>;
using value_type = range_value_t<T>;
using reference = range_reference_t<T>;
using size_type = range_size_t<T>;
private:
T p_range;
std::decay_t<F> p_pred;
void advance_valid() {
while (!p_range.empty() && !p_pred(front())) {
p_range.pop_front();
}
}
public:
filter_range() = delete;
template<typename P>
filter_range(T const &range, P &&pred):
p_range(range), p_pred(std::forward<P>(pred))
{
advance_valid();
}
bool empty() const { return p_range.empty(); }
void pop_front() {
p_range.pop_front();
advance_valid();
}
range_reference_t<T> front() const { return p_range.front(); }
};
template<typename R, typename P>
using FilterPred = std::enable_if_t<std::is_same_v<
decltype(std::declval<P>()(std::declval<range_reference_t<R>>())), bool
>, P>;
} /* namespace detail */
/** @brief Gets a wrapper range that filters items by `pred`.
*
* The resulting range is ostd::forward_range_tag at most. The range will
* only contains items for which `pred` returns true. What this means is
* that upon creation, the given range is stored and all iterated until
* an item matching `pred` is reached. On `pop_front()`, this item is
* popped out and the same is done, i.e. again iterated until a new
* item matching `pred` is reached.
*
* In other words, this is done:
*
* ~~~{.cc}
* void advance(R &range, P &pred) {
* while (!range.empty() && !pred()) {
* range.pop_front();
* }
* }
*
* constructor(R range, P pred) {
* store_range_and_pred(range, pred);
* advance(stored_range, stored_pred);
* }
*
* void pop_front() {
* stored_range.pop_front();
* advance(stored_range, stored_pred);
* }
* ~~~
*
* The value, reference and size types are preserved, as are
* calls to `front()` and `empty()`.
*
* @see ostd::map()
*/
template<typename InputRange, typename Predicate>
inline auto filter(InputRange range, Predicate pred) {
return detail::filter_range<InputRange, Predicate>(range, std::move(pred));
}
/** @brief A pipeable version of ostd::filter().
*
* The `pred` is forwarded.
*/
template<typename Predicate>
inline auto filter(Predicate &&pred) {
return [pred = std::forward<Predicate>(pred)](auto &obj) mutable {
return filter(obj, std::forward<Predicate>(pred));
};
}
/** @} */
} /* namespace ostd */
#undef OSTD_TEST_MODULE
#endif
/** @} */
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