ah-functional.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
 
# include <gtest/gtest.h>
 
# include <ah-zip.H>
# include <ahFunctional.H>
# include <ah-string-utils.H>
# include <tpl_dynSetTree.H>
# include <tpl_odhash.H>
# include <tpl_dynArray.H>
 
using namespace std;
using namespace Aleph;
 
TEST(range, range_combs)
{
  EXPECT_EQ(range(0, 10), build_dynlist<int>(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
  EXPECT_EQ(range(0, 10, 2), build_dynlist<int>(0, 2, 4, 6, 8, 10));
  EXPECT_EQ(nrange(2, 5, 3), build_dynlist<int>(2, 3, 5));
  EXPECT_EQ(contiguous_range(1, 5), build_dynlist<int>(1, 2, 3, 4, 5));
  EXPECT_EQ(range(5), build_dynlist<int>(0, 1, 2, 3, 4));
}
 
TEST(rep, rep)
{
  EXPECT_EQ(rep(5, 0), build_dynlist<int>(0, 0, 0, 0, 0));
  EXPECT_EQ(rep(3), build_dynlist<int>(0, 0, 0));
}
 
TEST(set_range, set_range_with_op)
{
  auto sq = [] (int x) { return x * x; };
  auto r = set_range<int, DynList>(0, 4, 1, sq);
  EXPECT_EQ(r, build_dynlist<int>(0, 1, 4, 9, 16));
 
  auto r2 = set_range<int, DynList>(0, 6, 2, sq);
  EXPECT_EQ(r2, build_dynlist<int>(0, 4, 16, 36));
}
 
TEST(each, each_variations)
{
  size_t count = 0;
  each(5, [&count] () { ++count; });
  EXPECT_EQ(count, 5);
 
  count = 0;
  each(2, 5, [&count] () { ++count; });
  EXPECT_EQ(count, 4);
}
 
struct TreeContainer : testing::Test
{
  static constexpr size_t N = 10;
  DynSetTree<size_t> tbl;
  TreeContainer()
  {
    tbl = range<size_t>(0, N - 1);
  }
};
 
TEST_F(TreeContainer, pointers)
{
  auto l = pointers_list(tbl);
 
  size_t i = 0;
  for (auto it = l.get_it(); it.has_curr(); it.next_ne(), ++i)
    EXPECT_EQ(*it.get_curr_ne(), i);
 
  EXPECT_TRUE(zip_all([] (auto t) { return *get<0>(t) == get<1>(t); }, l, tbl));
}
 
TEST_F(TreeContainer, sublist)
{
  EXPECT_EQ(sublist(tbl, 2), build_dynlist<size_t>(0, 2, 4, 6, 8));
  EXPECT_EQ(sublist(tbl, 1, 3), build_dynlist<size_t>(1, 4, 7));
}
 
TEST_F(TreeContainer, ml)
{
  size_t i = 0;
  for_each(tbl, [&i] (auto & k)
     {
       EXPECT_EQ(i++, k);
     });
 
  enum_for_each(tbl, ([] (auto & k, auto & i)
         {
     EXPECT_EQ(i, k);
         }));
 
  i = 0;
  EXPECT_TRUE(all(tbl, [&i] (auto & k) { return k == i++; }));
 
  EXPECT_TRUE(exists(tbl, [] (auto & i) { return i == 3; }));
  EXPECT_FALSE(exists(tbl, [] (auto & i) { return i == N; }));
 
  auto lfilt = filter(tbl, [] (auto & i) { return i <= 3; });
  EXPECT_EQ(lfilt, build_dynlist<size_t>(0, 1, 2, 3));
 
  auto lp = maps<string>(tbl, [] (const auto & i) { return to_string(i); });
  EXPECT_EQ(lp, build_dynlist<string>
      ("0", "1", "2", "3", "4", "5", "6", "7", "8", "9"));
 
  auto lf = foldl<size_t>(tbl, 0, [] (auto & a, auto & i) { return a + i; });
  EXPECT_EQ(lf, N*(N - 1)/2);
}
 
TEST_F(TreeContainer, gen_seq_list_tuples)
{
  auto l = gen_seq_list_tuples(tbl, 7);
  EXPECT_EQ(l, build_dynlist<DynList<size_t>>
      ( build_dynlist<size_t>(0, 1, 2, 3, 4, 5, 6),
        build_dynlist<size_t>(1, 2, 3, 4, 5, 6, 7),
        build_dynlist<size_t>(2, 3, 4, 5, 6, 7, 8),
        build_dynlist<size_t>(3, 4, 5, 6, 7, 8, 9) ));
}
 
TEST_F(TreeContainer, enumerate)
{
  auto l = enumerate(tbl);
  EXPECT_TRUE(l.all([] (auto & p) { return p.first == p.second; }));
}
 
TEST_F(TreeContainer, indexes_and_tindexes)
{
  auto idx = indexes(tbl);
  size_t i = 0;
  for (auto it = idx.get_it(); it.has_curr(); it.next_ne(), ++i)
    {
      auto & p = it.get_curr();
      EXPECT_EQ(p.first, i);
      EXPECT_EQ(p.second, i);
    }
 
  auto tidx = tindexes(tbl);
  i = 0;
  for (auto it = tidx.get_it(); it.has_curr(); it.next_ne(), ++i)
    {
      auto & t = it.get_curr();
      EXPECT_EQ(get<0>(t), i);
      EXPECT_EQ(get<1>(t), i);
    }
}
 
TEST_F(TreeContainer, reverse_test)
{
  DynList<size_t> l = range<size_t>(0, N - 1);
  auto rev = reverse(l);
  EXPECT_EQ(rev, build_dynlist<size_t>(9, 8, 7, 6, 5, 4, 3, 2, 1, 0));
}
 
TEST_F(TreeContainer, partition_test)
{
  auto p = partition(tbl, [] (const size_t & i) { return i < 5; });
  EXPECT_EQ(p.first, build_dynlist<size_t>(0, 1, 2, 3, 4));
  EXPECT_EQ(p.second, build_dynlist<size_t>(5, 6, 7, 8, 9));
}
 
TEST_F(TreeContainer, diff_test)
{
  DynList<size_t> l1 = range<size_t>(0, N - 1);
  DynList<size_t> l2 = range<size_t>(0, N - 1);
  EXPECT_FALSE(diff(l1, l2));
 
  l2.get_last() = 100;
  EXPECT_TRUE(diff(l1, l2));
}
 
TEST_F(TreeContainer, containers_eq_test)
{
  DynList<size_t> l = range<size_t>(0, N - 1);
  EXPECT_TRUE(containers_eq(tbl, l, std::equal_to<size_t>()));
}
 
TEST(Compare, comparisons)
{
  constexpr size_t N = 20;
  DynList<size_t> l1 = range(N);
  DynList<size_t> l2 = range(N + 1);
  DynSetTree<size_t> s1 = range(N);
  DynSetTree<size_t> s2 = range(N + 1);
 
  EXPECT_TRUE(eq(l1, s1));
  EXPECT_TRUE(lesser(l1, l2));
  EXPECT_TRUE(lesser(l1, s2));
  EXPECT_FALSE(lesser(l1, s1));
  EXPECT_FALSE(lesser(s1, l1));
 
  auto d = are_eq(l1, s1);
  EXPECT_TRUE(get<0>(d));
  EXPECT_EQ(get<1>(d), N);
 
  // Now we modify the last item of l1
  l1.get_last() = N - 2;
  EXPECT_FALSE(eq(l1, s1));
  EXPECT_TRUE(lesser(l1, s1));
 
  d = are_eq(l1, s1);
  EXPECT_FALSE(get<0>(d));
  EXPECT_EQ(get<1>(d), N - 1);
  EXPECT_EQ(get<2>(d), N - 2);
  EXPECT_EQ(get<3>(d), N - 1);
}
 
TEST_F(TreeContainer, zips)
{
  {
    auto z = zip(tbl, range(N));
    EXPECT_TRUE(z.all([] (auto & p) { return p.first == p.second; }));
 
    auto p = unzip(z);
    EXPECT_TRUE(zip_all([] (auto p) { return get<0>(p) == get<1>(p); },
      p.first, p.second));
  }
  {
    auto z = tzip(tbl, range(N));
    EXPECT_TRUE(z.all([] (auto & p) { return get<0>(p) == get<1>(p); }));
 
    auto p = tunzip(z);
    EXPECT_TRUE(zip_all([] (auto p) { return get<0>(p) == get<1>(p); },
      get<0>(p), get<1>(p)));
  }
  {
    auto z = zipEq(tbl, range(N));
    EXPECT_TRUE(z.all([] (auto & p) { return p.first == p.second; }));
 
    EXPECT_THROW(zipEq(tbl, range(N + 1)), length_error);
 
    auto p = unzip(z);
    EXPECT_TRUE(zip_all([] (auto p) { return get<0>(p) == get<1>(p); },
        p.first, p.second));
  }
  {
    auto z = tzipEq(tbl, range(N));
    EXPECT_TRUE(z.all([] (auto & p) { return get<0>(p) == get<1>(p); }));
 
    EXPECT_THROW(tzipEq(tbl, range(N + 1)), length_error);
 
    auto p = tunzip(z);
    EXPECT_TRUE(zip_all([] (auto p) { return get<0>(p) == get<1>(p); },
        get<0>(p), get<1>(p)));
  }
}
 
TEST(sequential_groups_test, sequential_groups)
{
  DynList<int> l = build_dynlist<int>(1, 1, 2, 2, 2, 4, 4, 0, 0, 1);
  auto result = sequential_groups(l);
  EXPECT_EQ(result.second, 5);
  auto & groups = result.first;
 
  auto it = groups.get_it();
  EXPECT_EQ(it.get_curr(), build_dynlist<int>(1, 1)); it.next();
  EXPECT_EQ(it.get_curr(), build_dynlist<int>(2, 2, 2)); it.next();
  EXPECT_EQ(it.get_curr(), build_dynlist<int>(4, 4)); it.next();
  EXPECT_EQ(it.get_curr(), build_dynlist<int>(0, 0)); it.next();
  EXPECT_EQ(it.get_curr(), build_dynlist<int>(1));
 
  // Empty container
  DynList<int> empty;
  auto empty_result = sequential_groups(empty);
  EXPECT_EQ(empty_result.second, 0);
  EXPECT_TRUE(empty_result.first.is_empty());
}
 
TEST(unique_sequential_test, unique_sequential)
{
  DynList<int> l = build_dynlist<int>(1, 1, 2, 2, 2, 4, 4, 0, 0, 1);
  auto result = unique_sequential(l);
  EXPECT_EQ(result.second, 5);
  EXPECT_EQ(result.first, build_dynlist<int>(1, 2, 4, 0, 1));
 
  // Empty container
  DynList<int> empty;
  auto empty_result = unique_sequential(empty);
  EXPECT_EQ(empty_result.second, 0);
  EXPECT_TRUE(empty_result.first.is_empty());
}
 
TEST(pair_iterator_test, pair_iterator)
{
  DynList<int> l1 = range(5);
  DynList<int> l2 = range(5);
 
  auto pit = get_pair_it(l1, l2);
  size_t i = 0;
  while (pit.has_curr())
    {
      auto p = pit.get_curr();
      EXPECT_EQ(p.first, i);
      EXPECT_EQ(p.second, i);
      pit.next();
      ++i;
    }
  EXPECT_EQ(i, 5);
  EXPECT_TRUE(pit.was_traversed());
 
  // Test with position
  auto pit2 = get_pair_it(l1, l2, 2);
  auto p = pit2.get_curr();
  EXPECT_EQ(p.first, 2);
  EXPECT_EQ(p.second, 2);
}
 
TEST(container_ops, insert_append_remove)
{
  DynList<int> c;
  size_t n = append_in_container(c, 1, 2, 3);
  EXPECT_EQ(n, 3);
  EXPECT_EQ(c, build_dynlist<int>(1, 2, 3));
 
  DynSetTree<int> s;
  n = insert_in_container(s, 5, 3, 1, 4, 2);
  EXPECT_EQ(n, 5);
  EXPECT_EQ(s.size(), 5);
 
  n = remove_from_container(s, 1, 2, 3);
  EXPECT_EQ(n, 3);
  EXPECT_EQ(s.size(), 2);
}
 
TEST(assign_container_test, assign_container)
{
  DynList<int> src = build_dynlist<int>(1, 2, 3, 4, 5);
  auto dst = assign_container<DynList<int>, DynList<int>>(src);
  EXPECT_EQ(src, dst);
}
 
TEST(flatten_test, flatten)
{
  DynList<DynList<int>> ll;
  ll.append(build_dynlist<int>(1, 2, 3));
  ll.append(build_dynlist<int>(4, 5));
  ll.append(build_dynlist<int>(6, 7, 8, 9));
 
  auto flat = flatten(ll);
  EXPECT_EQ(flat, build_dynlist<int>(1, 2, 3, 4, 5, 6, 7, 8, 9));
}
 
TEST(is_inside_test, is_inside)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 7, 9);
  EXPECT_TRUE(is_inside(3, l));
  EXPECT_TRUE(is_inside(9, l));
  EXPECT_FALSE(is_inside(2, l));
  EXPECT_FALSE(is_inside(10, l));
}
 
TEST(is_equal_test, is_equal)
{
  EXPECT_TRUE(is_equal(5, 3, 5, 7));
  EXPECT_TRUE(is_equal(5, 5));
  EXPECT_FALSE(is_equal(5, 1, 2, 3, 4));
  EXPECT_FALSE(is_equal(5));
 
  // Mixed types
  EXPECT_TRUE(is_equal(5, 5.0));
  EXPECT_TRUE(is_equal(5, 3, 5.0, 7));
}
 
TEST(FoundItem, FoundItemTests)
{
  int val = 42;
  Some<int> s(val);
  EXPECT_TRUE(s.is_found());
  EXPECT_EQ(s.get_item(), 42);
  s.get_item() = 43;
  EXPECT_EQ(val, 43);
 
  None<int> n;
  EXPECT_FALSE(n.is_found());
  EXPECT_THROW(n.get_item(), std::logic_error);
 
  const None<int> cn;
  EXPECT_THROW(cn.get_item(), std::logic_error);
 
  const Some<int> cs(val);
  EXPECT_EQ(cs.get_item(), 43);
}
 
TEST(range, range_precision)
{
  // Floating point nrange
  auto r = nrange<double, DynList>(0.0, 1.0, 11);
  EXPECT_EQ(r.size(), 11u);
  EXPECT_DOUBLE_EQ(r.get_first(), 0.0);
  EXPECT_DOUBLE_EQ(r.get_last(), 1.0);
  EXPECT_DOUBLE_EQ(r.nth(5), 0.5);
 
  // n=1 case
  auto r1 = nrange<int, DynList>(10, 20, 1);
  ASSERT_EQ(r1.size(), 1u);
  EXPECT_EQ(r1.get_first(), 10);
 
  // n=0 case
  EXPECT_THROW(nrange(0, 10, 0), std::domain_error);
}
 
TEST(flatten_test, flatten_deep)
{
  DynList<DynList<DynList<int>>> lll;
  lll.append(build_dynlist<DynList<int>>(build_dynlist<int>(1, 2), build_dynlist<int>(3)));
  lll.append(build_dynlist<DynList<int>>(build_dynlist<int>(4, 5, 6)));
 
  auto flat = flatten(lll);
  EXPECT_EQ(flat, build_dynlist<int>(1, 2, 3, 4, 5, 6));
 
  DynList<DynList<DynList<DynList<int>>>> llll;
  llll.append(lll);
  auto flat4 = flatten(llll);
  EXPECT_EQ(flat4, build_dynlist<int>(1, 2, 3, 4, 5, 6));
}
 
TEST(each_test, each_edge)
{
  size_t count = 0;
  each(0, [&count] () { ++count; });
  EXPECT_EQ(count, 0);
 
  count = 0;
  each(1, [&count] () { ++count; });
  EXPECT_EQ(count, 1);
}
 
// Tests for new functions
 
TEST(none_test, none_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
  EXPECT_TRUE(none(l, [] (int x) { return x > 10; }));
  EXPECT_FALSE(none(l, [] (int x) { return x == 3; }));
 
  DynList<int> empty;
  EXPECT_TRUE(none(empty, [] (int) { return true; }));
}
 
TEST(find_ptr_test, find_ptr_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  auto * p = find_ptr(l, [] (int x) { return x == 3; });
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 3);
 
  // Modify through pointer
  *p = 30;
  EXPECT_EQ(l.nth(2), 30);
 
  auto * not_found = find_ptr(l, [] (int x) { return x == 100; });
  EXPECT_EQ(not_found, nullptr);
 
  // const version
  const DynList<int> cl = build_dynlist<int>(10, 20, 30);
  const int * cp = find_ptr(cl, [] (int x) { return x == 20; });
  ASSERT_NE(cp, nullptr);
  EXPECT_EQ(*cp, 20);
}
 
TEST(foldr_test, foldr_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4);
 
  // foldr with subtraction: 1 - (2 - (3 - (4 - 0))) = 1 - (2 - (3 - 4)) = 1 - (2 - (-1)) = 1 - 3 = -2
  auto result = foldr<int>(l, 0, [] (int a, int b) { return a - b; });
  EXPECT_EQ(result, -2);
 
  // Compare with foldl: ((((0 - 1) - 2) - 3) - 4) = -10
  auto result_l = foldl<int>(l, 0, [] (int a, int b) { return a - b; });
  EXPECT_EQ(result_l, -10);
}
 
TEST(sum_product_test, sum_product_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
  EXPECT_EQ(sum(l), 15);
  EXPECT_EQ(sum(l, 10), 25);
 
  EXPECT_EQ(product(l), 120);
  EXPECT_EQ(product(l, 2), 240);
 
  DynList<int> empty;
  EXPECT_EQ(sum(empty), 0);
  EXPECT_EQ(product(empty), 1);
 
  DynList<double> ld = build_dynlist<double>(1.5, 2.5, 3.0);
  EXPECT_DOUBLE_EQ(sum(ld), 7.0);
}
 
TEST(concat_test, concat_basic)
{
  DynList<int> l1 = build_dynlist<int>(1, 2, 3);
  DynList<int> l2 = build_dynlist<int>(4, 5, 6);
 
  auto c = concat(l1, l2);
  EXPECT_EQ(c, build_dynlist<int>(1, 2, 3, 4, 5, 6));
 
  DynList<int> empty;
  EXPECT_EQ(concat(empty, l1), l1);
  EXPECT_EQ(concat(l1, empty), l1);
}
 
TEST(take_while_test, take_while_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 10, 5, 6);
 
  auto result = take_while(l, [] (int x) { return x < 5; });
  EXPECT_EQ(result, build_dynlist<int>(1, 2, 3));
 
  // All elements satisfy
  auto all = take_while(l, [] (int) { return true; });
  EXPECT_EQ(all, l);
 
  // No elements satisfy
  auto none_result = take_while(l, [] (int x) { return x > 100; });
  EXPECT_TRUE(none_result.is_empty());
}
 
TEST(drop_while_test, drop_while_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 10, 5, 6);
 
  auto result = drop_while(l, [] (int x) { return x < 5; });
  EXPECT_EQ(result, build_dynlist<int>(10, 5, 6));
 
  // All elements satisfy - drop all
  auto all_dropped = drop_while(l, [] (int) { return true; });
  EXPECT_TRUE(all_dropped.is_empty());
 
  // No elements satisfy - keep all
  auto none_dropped = drop_while(l, [] (int x) { return x > 100; });
  EXPECT_EQ(none_dropped, l);
}
 
TEST(flat_map_test, flat_map_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  // Duplicate each element
  auto result = flat_map(l, [] (int x) {
    return build_dynlist<int>(x, x);
  });
  EXPECT_EQ(result, build_dynlist<int>(1, 1, 2, 2, 3, 3));
 
  // Create range for each
  auto ranges = flat_map(l, [] (int x) {
    return range(x);
  });
  EXPECT_EQ(ranges, build_dynlist<int>(0, 0, 1, 0, 1, 2));
}
 
TEST(scanl_test, scanl_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4);
 
  auto sums = scanl<int>(l, 0, [] (int a, int b) { return a + b; });
  EXPECT_EQ(sums, build_dynlist<int>(0, 1, 3, 6, 10));
 
  auto sums2 = scanl_sum(l, 0);
  EXPECT_EQ(sums2, build_dynlist<int>(0, 1, 3, 6, 10));
 
  DynList<int> empty;
  auto empty_scan = scanl<int>(empty, 100, [] (int a, int b) { return a + b; });
  EXPECT_EQ(empty_scan, build_dynlist<int>(100));
}
 
TEST(min_max_test, min_max_basic)
{
  DynList<int> l = build_dynlist<int>(5, 2, 8, 1, 9, 3);
 
  auto * min_p = min_ptr(l);
  ASSERT_NE(min_p, nullptr);
  EXPECT_EQ(*min_p, 1);
 
  auto * max_p = max_ptr(l);
  ASSERT_NE(max_p, nullptr);
  EXPECT_EQ(*max_p, 9);
 
  auto [minp, maxp] = minmax_ptr(l);
  ASSERT_NE(minp, nullptr);
  ASSERT_NE(maxp, nullptr);
  EXPECT_EQ(*minp, 1);
  EXPECT_EQ(*maxp, 9);
 
  // Empty container
  DynList<int> empty;
  EXPECT_EQ(min_ptr(empty), nullptr);
  EXPECT_EQ(max_ptr(empty), nullptr);
  auto [emp_min, emp_max] = minmax_ptr(empty);
  EXPECT_EQ(emp_min, nullptr);
  EXPECT_EQ(emp_max, nullptr);
 
  // Single element
  DynList<int> single = build_dynlist<int>(42);
  auto [s_min, s_max] = minmax_ptr(single);
  EXPECT_EQ(*s_min, 42);
  EXPECT_EQ(*s_max, 42);
 
  // Custom comparator
  DynList<int> abs_list = build_dynlist<int>(-10, 5, -20, 3);
  auto * max_abs = max_ptr(abs_list,
                           [] (const int a, const int b) { return std::abs(a) < std::abs(b); });
  EXPECT_EQ(*max_abs, -20);
}
 
TEST(count_if_test, count_if_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
 
  EXPECT_EQ(count_if(l, [] (int x) { return x % 2 == 0; }), 5);
  EXPECT_EQ(count_if(l, [] (int x) { return x > 5; }), 5);
  EXPECT_EQ(count_if(l, [] (int x) { return x > 100; }), 0);
 
  DynList<int> empty;
  EXPECT_EQ(count_if(empty, [] (int) { return true; }), 0);
}
 
TEST(contains_test, contains_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  EXPECT_TRUE(contains(l, 3));
  EXPECT_TRUE(contains(l, 1));
  EXPECT_TRUE(contains(l, 5));
  EXPECT_FALSE(contains(l, 0));
  EXPECT_FALSE(contains(l, 6));
 
  DynList<int> empty;
  EXPECT_FALSE(contains(empty, 1));
}
 
TEST(enumerate_tuple_test, enumerate_tuple_basic)
{
  DynList<string> l = build_dynlist<string>("a", "b", "c");
 
  auto result = enumerate_tuple(l);
  EXPECT_EQ(result.size(), 3);
 
  auto it = result.get_it();
  EXPECT_EQ(get<0>(it.get_curr()), 0);
  EXPECT_EQ(get<1>(it.get_curr()), "a");
  it.next();
  EXPECT_EQ(get<0>(it.get_curr()), 1);
  EXPECT_EQ(get<1>(it.get_curr()), "b");
  it.next();
  EXPECT_EQ(get<0>(it.get_curr()), 2);
  EXPECT_EQ(get<1>(it.get_curr()), "c");
}
 
// =============================================================================
// COMPREHENSIVE TESTS FOR ahFunctional.H
// =============================================================================
 
// --- zip_longest tests ---
 
TEST(zip_longest_test, basic_different_lengths)
{
  DynList<int> l1 = build_dynlist<int>(1, 2, 3, 4, 5);
  DynList<int> l2 = build_dynlist<int>(10, 20, 30);
 
  auto result = zip_longest(l1, l2, -1, -1);
  EXPECT_EQ(result.size(), 5);
 
  auto it = result.get_it();
  EXPECT_EQ(it.get_curr(), make_pair(1, 10)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(2, 20)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(3, 30)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(4, -1)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(5, -1));
}
 
TEST(zip_longest_test, second_longer)
{
  DynList<int> l1 = build_dynlist<int>(1, 2);
  DynList<int> l2 = build_dynlist<int>(10, 20, 30, 40);
 
  auto result = zip_longest(l1, l2, 0, 0);
  EXPECT_EQ(result.size(), 4);
 
  auto it = result.get_it();
  EXPECT_EQ(it.get_curr(), make_pair(1, 10)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(2, 20)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(0, 30)); it.next();
  EXPECT_EQ(it.get_curr(), make_pair(0, 40));
}
 
TEST(zip_longest_test, equal_lengths)
{
  DynList<int> l1 = build_dynlist<int>(1, 2, 3);
  DynList<int> l2 = build_dynlist<int>(4, 5, 6);
 
  auto result = zip_longest(l1, l2, -1, -1);
  EXPECT_EQ(result.size(), 3);
 
  EXPECT_TRUE(result.all([] (auto & p) {
    return p.first + 3 == p.second;
  }));
}
 
TEST(zip_longest_test, empty_containers)
{
  DynList<int> empty1, empty2;
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  auto r1 = zip_longest(empty1, empty2, 0, 0);
  EXPECT_TRUE(r1.is_empty());
 
  auto r2 = zip_longest(l, empty2, 0, -1);
  EXPECT_EQ(r2.size(), 3);
  EXPECT_TRUE(r2.all([] (auto & p) { return p.second == -1; }));
 
  auto r3 = zip_longest(empty1, l, -1, 0);
  EXPECT_EQ(r3.size(), 3);
  EXPECT_TRUE(r3.all([] (auto & p) { return p.first == -1; }));
}
 
// --- tzip_longest tests ---
 
TEST(tzip_longest_test, basic_different_lengths)
{
  DynList<int> l1 = build_dynlist<int>(1, 2, 3);
  DynList<string> l2 = build_dynlist<string>("a", "b");
 
  auto result = tzip_longest(l1, l2, 0, string("X"));
  EXPECT_EQ(result.size(), 3);
 
  auto it = result.get_it();
  EXPECT_EQ(get<0>(it.get_curr()), 1);
  EXPECT_EQ(get<1>(it.get_curr()), "a");
  it.next();
  EXPECT_EQ(get<0>(it.get_curr()), 2);
  EXPECT_EQ(get<1>(it.get_curr()), "b");
  it.next();
  EXPECT_EQ(get<0>(it.get_curr()), 3);
  EXPECT_EQ(get<1>(it.get_curr()), "X");
}
 
// --- zip_longest_opt tests ---
 
TEST(zip_longest_opt_test, basic_different_lengths)
{
  DynList<int> l1 = build_dynlist<int>(1, 2, 3, 4);
  DynList<int> l2 = build_dynlist<int>(10, 20);
 
  auto result = zip_longest_opt(l1, l2);
  EXPECT_EQ(result.size(), 4);
 
  auto it = result.get_it();
  auto p1 = it.get_curr();
  EXPECT_TRUE(p1.first.has_value());
  EXPECT_TRUE(p1.second.has_value());
  EXPECT_EQ(p1.first.value(), 1);
  EXPECT_EQ(p1.second.value(), 10);
 
  it.next(); it.next(); it.next();
  auto p4 = it.get_curr();
  EXPECT_TRUE(p4.first.has_value());
  EXPECT_FALSE(p4.second.has_value());
  EXPECT_EQ(p4.first.value(), 4);
}
 
// --- group_by tests ---
 
TEST(group_by_test, basic_grouping)
{
  DynList<int> l = build_dynlist<int>(1, 1, 2, 2, 2, 3, 1, 1);
 
  // group_by takes a key function that extracts the grouping key
  auto result = group_by(l, [] (int x) { return x; });
  EXPECT_EQ(result.size(), 4);
 
  auto it = result.get_it();
  // Each element is pair<key, DynList<T>>
  EXPECT_EQ(it.get_curr().first, 1);
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(1, 1));
  it.next();
  EXPECT_EQ(it.get_curr().first, 2);
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(2, 2, 2));
  it.next();
  EXPECT_EQ(it.get_curr().first, 3);
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(3));
  it.next();
  EXPECT_EQ(it.get_curr().first, 1);
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(1, 1));
}
 
TEST(group_by_test, group_by_parity)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 2, 4, 6, 7, 9);
 
  // Group by parity (consecutive groups with same parity)
  auto result = group_by(l, [] (int x) { return x % 2; });
  EXPECT_EQ(result.size(), 3);
 
  auto it = result.get_it();
  EXPECT_EQ(it.get_curr().first, 1);  // odd
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(1, 3, 5));
  it.next();
  EXPECT_EQ(it.get_curr().first, 0);  // even
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(2, 4, 6));
  it.next();
  EXPECT_EQ(it.get_curr().first, 1);  // odd again
  EXPECT_EQ(it.get_curr().second, build_dynlist<int>(7, 9));
}
 
TEST(group_by_test, empty_container)
{
  DynList<int> empty;
  auto result = group_by(empty, [] (int x) { return x; });
  EXPECT_TRUE(result.is_empty());
}
 
TEST(group_by_test, single_element)
{
  DynList<int> single = build_dynlist<int>(42);
  auto result = group_by(single, [] (int x) { return x; });
  EXPECT_EQ(result.size(), 1);
  EXPECT_EQ(result.get_first().first, 42);
  EXPECT_EQ(result.get_first().second, build_dynlist<int>(42));
}
 
// --- group_by_reduce tests ---
 
TEST(group_by_reduce_test, sum_groups)
{
  DynList<int> l = build_dynlist<int>(1, 1, 2, 2, 2, 3);
 
  auto result = group_by_reduce(l,
    [] (int x) { return x; },                        // key function
    [] (const DynList<int> & g) { return sum(g); }   // reducer (takes group)
  );
 
  // Result should be list of (key, reduced_value) pairs
  EXPECT_EQ(result.size(), 3);
 
  auto it = result.get_it();
  // First group: key=1, sum=1+1=2
  EXPECT_EQ(it.get_curr().first, 1);
  EXPECT_EQ(it.get_curr().second, 2);
  it.next();
  // Second group: key=2, sum=2+2+2=6
  EXPECT_EQ(it.get_curr().first, 2);
  EXPECT_EQ(it.get_curr().second, 6);
  it.next();
  // Third group: key=3, sum=3
  EXPECT_EQ(it.get_curr().first, 3);
  EXPECT_EQ(it.get_curr().second, 3);
}
 
// --- maps and maps_if tests ---
 
TEST(maps_test, basic_map)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  auto result = maps<int>(l, [] (int x) { return x * x; });
  EXPECT_EQ(result, build_dynlist<int>(1, 4, 9, 16, 25));
}
 
TEST(maps_test, type_conversion)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  auto result = maps<string>(l, [] (int x) { return to_string(x); });
  EXPECT_EQ(result, build_dynlist<string>("1", "2", "3"));
}
 
TEST(filter_map_test, conditional_map)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5, 6);
 
  // Filter then map: square only even numbers
  auto filtered = filter(l, [] (int x) { return x % 2 == 0; });
  auto result = maps<int>(filtered, [] (int x) { return x * x; });
 
  EXPECT_EQ(result, build_dynlist<int>(4, 16, 36));
}
 
TEST(filter_map_test, no_matches)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 7);
 
  auto filtered = filter(l, [] (int x) { return x % 2 == 0; });
  auto result = maps<int>(filtered, [] (int x) { return x * 2; });
 
  EXPECT_TRUE(result.is_empty());
}
 
// --- split tests using DynList split method ---
 
TEST(split_test, basic_split)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5, 6);
 
  // Use take and drop to simulate split at position 3
  auto left = l.take(3);
  auto right = l.drop(3);
 
  EXPECT_EQ(left, build_dynlist<int>(1, 2, 3));
  EXPECT_EQ(right, build_dynlist<int>(4, 5, 6));
}
 
// --- take and drop comprehensive tests ---
 
TEST(take_drop_test, take_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  EXPECT_EQ(l.take(3), build_dynlist<int>(1, 2, 3));
  EXPECT_EQ(l.take(0), DynList<int>());
  EXPECT_EQ(l.take(10), l);
}
 
TEST(take_drop_test, drop_basic)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  EXPECT_EQ(l.drop(2), build_dynlist<int>(3, 4, 5));
  EXPECT_EQ(l.drop(0), l);
  EXPECT_EQ(l.drop(10), DynList<int>());
}
 
TEST(take_drop_test, take_drop_range)
{
  DynList<int> l = build_dynlist<int>(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
 
  // Take elements from position 3 to 7
  auto result = l.take(3, 7);
  EXPECT_EQ(result, build_dynlist<int>(3, 4, 5, 6, 7));
}
 
// --- to_dynlist tests ---
 
TEST(to_dynlist_test, from_tree)
{
  DynSetTree<int> tree;
  for (int i = 0; i < 5; ++i)
    tree.insert(i);
 
  auto list = to_dynlist(tree);
  EXPECT_EQ(list.size(), 5);
  EXPECT_EQ(list, build_dynlist<int>(0, 1, 2, 3, 4));
}
 
TEST(to_dynlist_test, from_array)
{
  DynArray<int> arr;
  for (int i = 0; i < 5; ++i)
    arr.append(i * 2);
 
  auto list = to_dynlist(arr);
  EXPECT_EQ(list.size(), 5);
  EXPECT_EQ(list, build_dynlist<int>(0, 2, 4, 6, 8));
}
 
// --- traverse with filter test ---
 
TEST(traverse_filter_test, count_evens)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
 
  size_t count = 0;
  l.traverse([&count] (int x) {
    if (x % 2 == 0) ++count;
    return true;
  });
 
  EXPECT_EQ(count, 5);
}
 
// --- Edge cases and stress tests ---
 
TEST(functional_stress_test, large_container)
{
  constexpr size_t N = 10000;
  DynList<size_t> l = range<size_t>(N);
 
  // Test foldl on large container
  auto sum = foldl<size_t>(l, 0, [] (size_t a, size_t b) { return a + b; });
  EXPECT_EQ(sum, N * (N - 1) / 2);
 
  // Test filter on large container
  auto evens = filter(l, [] (size_t x) { return x % 2 == 0; });
  EXPECT_EQ(evens.size(), N / 2);
 
  // Test maps on large container
  auto doubled = maps<size_t>(l, [] (size_t x) { return x * 2; });
  EXPECT_EQ(doubled.size(), N);
  EXPECT_EQ(doubled.get_first(), 0);
  EXPECT_EQ(doubled.get_last(), (N - 1) * 2);
}
 
TEST(functional_stress_test, chained_operations)
{
  DynList<int> l = range(100);
 
  // Chain: filter even -> map square -> take first 5 -> sum
  auto result = filter(l, [] (int x) { return x % 2 == 0; });  // 50 evens
  auto squared = maps<int>(result, [] (int x) { return x * x; });
  auto first5 = squared.take(5);  // 0, 4, 16, 36, 64
  auto total = sum(first5);
 
  EXPECT_EQ(total, 0 + 4 + 16 + 36 + 64);
}
 
TEST(functional_edge_test, empty_container_operations)
{
  DynList<int> empty;
 
  // All these should handle empty containers gracefully
  EXPECT_TRUE(filter(empty, [] (int) { return true; }).is_empty());
  EXPECT_TRUE(maps<int>(empty, [] (int x) { return x; }).is_empty());
  EXPECT_EQ(foldl<int>(empty, 42, [] (int a, int b) { return a + b; }), 42);
  EXPECT_TRUE(all(empty, [] (int) { return false; }));  // vacuously true
  EXPECT_FALSE(exists(empty, [] (int) { return true; }));
  EXPECT_TRUE(none(empty, [] (int) { return true; }));
  EXPECT_EQ(sum(empty), 0);
  EXPECT_EQ(product(empty), 1);
  EXPECT_TRUE(reverse(empty).is_empty());
}
 
TEST(functional_edge_test, single_element)
{
  DynList<int> single = build_dynlist<int>(42);
 
  EXPECT_EQ(filter(single, [] (int x) { return x > 0; }).size(), 1);
  EXPECT_EQ(maps<int>(single, [] (int x) { return x * 2; }).get_first(), 84);
  EXPECT_EQ(sum(single), 42);
  EXPECT_EQ(product(single), 42);
  EXPECT_EQ(reverse(single).get_first(), 42);
  EXPECT_EQ(*min_ptr(single), 42);
  EXPECT_EQ(*max_ptr(single), 42);
}
 
// --- Complex type tests ---
 
struct Person
{
  string name;
  int age;
 
  bool operator==(const Person & other) const
  {
    return name == other.name && age == other.age;
  }
};
 
TEST(functional_complex_type_test, struct_operations)
{
  DynList<Person> people;
  people.append({"Alice", 30});
  people.append({"Bob", 25});
  people.append({"Charlie", 35});
  people.append({"Diana", 28});
 
  // Filter by age
  auto over28 = filter(people, [] (const Person & p) { return p.age > 28; });
  EXPECT_EQ(over28.size(), 2);
 
  // Map to names
  auto names = maps<string>(people, [] (const Person & p) { return p.name; });
  EXPECT_EQ(names, build_dynlist<string>("Alice", "Bob", "Charlie", "Diana"));
 
  // Find oldest
  auto * oldest = max_ptr(people, [] (const Person & a, const Person & b) {
    return a.age < b.age;
  });
  ASSERT_NE(oldest, nullptr);
  EXPECT_EQ(oldest->name, "Charlie");
 
  // Sum of ages
  auto total_age = foldl<int>(people, 0, [] (int acc, const Person & p) {
    return acc + p.age;
  });
  EXPECT_EQ(total_age, 30 + 25 + 35 + 28);
}
 
// --- Lazy evaluation / composition tests ---
 
TEST(functional_composition_test, nested_maps)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  // map twice
  auto result = maps<int>(maps<int>(l, [] (int x) { return x + 1; }),
                          [] (int x) { return x * x; });
  EXPECT_EQ(result, build_dynlist<int>(4, 9, 16));  // (1+1)^2, (2+1)^2, (3+1)^2
}
 
TEST(functional_composition_test, filter_then_map)
{
  DynList<int> l = range(10);
 
  auto result = maps<string>(
    filter(l, [] (int x) { return x % 3 == 0; }),
    [] (int x) { return "val" + to_string(x); }
  );
 
  EXPECT_EQ(result, build_dynlist<string>("val0", "val3", "val6", "val9"));
}
 
// --- Quantifier tests ---
 
TEST(quantifier_test, all_comprehensive)
{
  DynList<int> l = build_dynlist<int>(2, 4, 6, 8, 10);
 
  EXPECT_TRUE(all(l, [] (int x) { return x % 2 == 0; }));  // all even
  EXPECT_TRUE(all(l, [] (int x) { return x > 0; }));       // all positive
  EXPECT_FALSE(all(l, [] (int x) { return x > 5; }));      // not all > 5
 
  // Empty container - vacuously true
  DynList<int> empty;
  EXPECT_TRUE(all(empty, [] (int) { return false; }));
}
 
TEST(quantifier_test, exists_comprehensive)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 6, 7);
 
  EXPECT_TRUE(exists(l, [] (int x) { return x % 2 == 0; }));   // 6 is even
  EXPECT_TRUE(exists(l, [] (int x) { return x == 7; }));       // 7 exists
  EXPECT_FALSE(exists(l, [] (int x) { return x > 100; }));     // none > 100
 
  // Empty container - false
  DynList<int> empty;
  EXPECT_FALSE(exists(empty, [] (int) { return true; }));
}
 
TEST(quantifier_test, none_comprehensive)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 7, 9);
 
  EXPECT_TRUE(none(l, [] (int x) { return x % 2 == 0; }));   // no even
  EXPECT_TRUE(none(l, [] (int x) { return x > 100; }));      // none > 100
  EXPECT_FALSE(none(l, [] (int x) { return x == 5; }));      // 5 exists
 
  // Empty container - vacuously true
  DynList<int> empty;
  EXPECT_TRUE(none(empty, [] (int) { return true; }));
}
 
// =============================================================================
// Additional comprehensive tests
// =============================================================================
 
// --- scanl comprehensive tests ---
 
TEST(scanl_comprehensive, scanl_sum_variants)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3, 4, 5);
 
  // Basic scanl_sum starting from 0
  auto sums = scanl_sum(l, 0);
  EXPECT_EQ(sums, build_dynlist<int>(0, 1, 3, 6, 10, 15));
 
  // scanl_sum with non-zero init
  auto sums2 = scanl_sum(l, 100);
  EXPECT_EQ(sums2, build_dynlist<int>(100, 101, 103, 106, 110, 115));
 
  // Empty container
  DynList<int> empty;
  auto empty_scan = scanl_sum(empty, 42);
  EXPECT_EQ(empty_scan.size(), 1);
  EXPECT_EQ(empty_scan.get_first(), 42);
}
 
TEST(scanl_comprehensive, scanl_custom_op)
{
  DynList<int> l = build_dynlist<int>(2, 3, 4);
 
  // Product scan
  auto products = scanl<int>(l, 1, [] (int acc, int x) { return acc * x; });
  EXPECT_EQ(products, build_dynlist<int>(1, 2, 6, 24));
 
  // Max scan
  auto maxes = scanl<int>(l, 0, [] (int acc, int x) { return std::max(acc, x); });
  EXPECT_EQ(maxes, build_dynlist<int>(0, 2, 3, 4));
}
 
// --- flat_map comprehensive tests ---
 
TEST(flat_map_comprehensive, basic_operations)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  // Expand each number to a range
  auto result = flat_map(l, [] (int x) {
    return range(x);  // 0..x-1
  });
  // 1 -> {0}, 2 -> {0,1}, 3 -> {0,1,2}
  EXPECT_EQ(result, build_dynlist<int>(0, 0, 1, 0, 1, 2));
}
 
TEST(flat_map_comprehensive, replicate_pattern)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  // Replicate each element by its value
  auto result = flat_map(l, [] (int x) -> DynList<int> {
    DynList<int> res;
    for (int i = 0; i < x; ++i)
      res.append(x);
    return res;
  });
  EXPECT_EQ(result, build_dynlist<int>(1, 2, 2, 3, 3, 3));
}
 
TEST(flat_map_comprehensive, empty_inner)
{
  DynList<int> l = build_dynlist<int>(1, 2, 3);
 
  // Some inner results are empty
  auto result = flat_map(l, [] (int x) {
    if (x % 2 == 0)
      return DynList<int>();
    return build_dynlist<int>(x);
  });
  EXPECT_EQ(result, build_dynlist<int>(1, 3));
}
 
// --- concat comprehensive tests ---
 
TEST(concat_comprehensive, various_combinations)
{
  DynList<int> a = build_dynlist<int>(1, 2);
  DynList<int> b = build_dynlist<int>(3, 4, 5);
  DynList<int> empty;
 
  EXPECT_EQ(concat(a, b), build_dynlist<int>(1, 2, 3, 4, 5));
  EXPECT_EQ(concat(empty, b), build_dynlist<int>(3, 4, 5));
  EXPECT_EQ(concat(a, empty), build_dynlist<int>(1, 2));
  EXPECT_EQ(concat(empty, empty), DynList<int>());
}
 
// --- take_while / drop_while comprehensive tests ---
 
TEST(while_comprehensive, take_while_various)
{
  DynList<int> l = build_dynlist<int>(2, 4, 6, 7, 8, 10);
 
  // Take while even
  auto evens = take_while(l, [] (int x) { return x % 2 == 0; });
  EXPECT_EQ(evens, build_dynlist<int>(2, 4, 6));
 
  // Take while < 5
  auto small = take_while(l, [] (int x) { return x < 5; });
  EXPECT_EQ(small, build_dynlist<int>(2, 4));
 
  // Take nothing (first element fails)
  auto none_taken = take_while(l, [] (int x) { return x > 100; });
  EXPECT_TRUE(none_taken.is_empty());
 
  // Take all
  auto all_taken = take_while(l, [] (int) { return true; });
  EXPECT_EQ(all_taken.size(), l.size());
}
 
TEST(while_comprehensive, drop_while_various)
{
  DynList<int> l = build_dynlist<int>(2, 4, 6, 7, 8, 10);
 
  // Drop while even
  auto after_evens = drop_while(l, [] (int x) { return x % 2 == 0; });
  EXPECT_EQ(after_evens, build_dynlist<int>(7, 8, 10));
 
  // Drop while < 5
  auto after_small = drop_while(l, [] (int x) { return x < 5; });
  EXPECT_EQ(after_small, build_dynlist<int>(6, 7, 8, 10));
 
  // Drop nothing (first element fails)
  auto none_dropped = drop_while(l, [] (int x) { return x > 100; });
  EXPECT_EQ(none_dropped.size(), l.size());
 
  // Drop all
  auto all_dropped = drop_while(l, [] (int) { return true; });
  EXPECT_TRUE(all_dropped.is_empty());
}
 
// --- reverse comprehensive tests ---
 
TEST(reverse_comprehensive, various_sizes)
{
  EXPECT_EQ(reverse(build_dynlist<int>(1)), build_dynlist<int>(1));
  EXPECT_EQ(reverse(build_dynlist<int>(1, 2)), build_dynlist<int>(2, 1));
  EXPECT_EQ(reverse(build_dynlist<int>(1, 2, 3)), build_dynlist<int>(3, 2, 1));
 
  DynList<int> empty;
  EXPECT_TRUE(reverse(empty).is_empty());
 
  // Reverse twice = original
  DynList<int> l = range(10);
  EXPECT_EQ(reverse(reverse(l)), l);
}
 
// --- min/max pointer comprehensive tests ---
 
TEST(min_max_ptr_comprehensive, with_comparator)
{
  DynList<string> names;
  names.append("Bob");
  names.append("Alice");
  names.append("Charlie");
 
  // By length
  auto * shortest = min_ptr(names, [] (const string & a, const string & b) {
    return a.length() < b.length();
  });
  ASSERT_NE(shortest, nullptr);
  EXPECT_EQ(*shortest, "Bob");
 
  auto * longest = max_ptr(names, [] (const string & a, const string & b) {
    return a.length() < b.length();
  });
  ASSERT_NE(longest, nullptr);
  EXPECT_EQ(*longest, "Charlie");
}
 
TEST(min_max_ptr_comprehensive, minmax_combined)
{
  DynList<int> l = build_dynlist<int>(3, 1, 4, 1, 5, 9, 2, 6);
 
  auto [min_p, max_p] = minmax_ptr(l);
  ASSERT_NE(min_p, nullptr);
  ASSERT_NE(max_p, nullptr);
  EXPECT_EQ(*min_p, 1);
  EXPECT_EQ(*max_p, 9);
}
 
// --- foldl/foldr comprehensive tests ---
 
TEST(fold_comprehensive, foldl_associativity)
{
  DynList<string> words;
  words.append("a");
  words.append("b");
  words.append("c");
 
  // foldl is left-associative: ((init op a) op b) op c
  auto result = foldl<string>(words, "START", [] (const string & acc, const string & x) {
    return "(" + acc + "+" + x + ")";
  });
  EXPECT_EQ(result, "(((START+a)+b)+c)");
}
 
TEST(fold_comprehensive, foldr_associativity)
{
  DynList<string> words;
  words.append("a");
  words.append("b");
  words.append("c");
 
  // foldr is right-associative: a op (b op (c op init))
  auto result = foldr<string>(words, "END", [] (const string & x, const string & acc) {
    return "(" + x + "+" + acc + ")";
  });
  EXPECT_EQ(result, "(a+(b+(c+END)))");
}
 
// --- zip comprehensive tests ---
 
TEST(zip_comprehensive, different_lengths)
{
  DynList<int> a = build_dynlist<int>(1, 2, 3, 4, 5);
  DynList<char> b;
  b.append('a');
  b.append('b');
 
  // Regular zip stops at shorter
  auto zipped = zip(a, b);
  EXPECT_EQ(zipped.size(), 2);
}
 
TEST(zip_comprehensive, zip_all_predicate)
{
  DynList<int> a = build_dynlist<int>(1, 2, 3);
  DynList<int> b = build_dynlist<int>(2, 4, 6);
 
  // Check if b[i] == 2*a[i] for all i
  bool all_double = zip_all([] (auto t) { return get<1>(t) == 2 * get<0>(t); }, a, b);
  EXPECT_TRUE(all_double);
 
  DynList<int> c = build_dynlist<int>(2, 4, 5);  // 5 != 2*3
  bool not_all = zip_all([] (auto t) { return get<1>(t) == 2 * get<0>(t); }, a, c);
  EXPECT_FALSE(not_all);
}
 
// --- group_by comprehensive tests ---
 
TEST(group_by_comprehensive, custom_key)
{
  DynList<int> l = build_dynlist<int>(1, 3, 5, 2, 4, 6, 7, 9);
 
  // Group by parity (odd=1, even=0)
  auto groups = group_by(l, [] (int x) { return x % 2; });
 
  EXPECT_EQ(groups.size(), 3);  // odd, even, odd groups
 
  auto it = groups.get_it();
  EXPECT_EQ(it.get_curr().first, 1);  // odd
  EXPECT_EQ(it.get_curr().second.size(), 3);  // 1, 3, 5
  it.next();
  EXPECT_EQ(it.get_curr().first, 0);  // even
  EXPECT_EQ(it.get_curr().second.size(), 3);  // 2, 4, 6
  it.next();
  EXPECT_EQ(it.get_curr().first, 1);  // odd
  EXPECT_EQ(it.get_curr().second.size(), 2);  // 7, 9
}
 
// --- Performance / stress tests ---
 
TEST(functional_performance, large_chain)
{
  constexpr size_t N = 10000;
  auto large = range<int>(0, static_cast<int>(N) - 1);
 
  // Chain: filter -> map -> sum (first 100 evens)
  auto evens = filter(large, [] (int x) { return x % 2 == 0; });
  auto squared = maps<int>(evens, [] (int x) { return x * x; });
 
  // Take first 100 elements manually
  DynList<int> first100;
  size_t count = 0;
  for (auto it = squared.get_it(); it.has_curr() && count < 100; it.next_ne(), ++count)
    first100.append(it.get_curr());
 
  // Sum of squares of first 100 even numbers: 0^2 + 2^2 + 4^2 + ... + 198^2
  long long expected = 0;
  for (int i = 0; i < 100; ++i)
    expected += (2LL * i) * (2LL * i);
 
  auto total = foldl<long long>(first100, 0LL, [] (long long acc, int x) {
    return acc + x;
  });
  EXPECT_EQ(total, expected);
}
 
TEST(functional_performance, deep_nesting)
{
  // Deeply nested maps
  auto l = range(5);
  auto result = maps<int>(
    maps<int>(
      maps<int>(l, [] (int x) { return x + 1; }),
      [] (int x) { return x * 2; }),
    [] (int x) { return x - 1; });
 
  // ((x + 1) * 2) - 1 for x in 0..4
  EXPECT_EQ(result, build_dynlist<int>(1, 3, 5, 7, 9));
}