CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.20)
 include(cmake/color.cmake)
-set(BLT_VERSION 1.1.8)
+set(BLT_VERSION 1.1.7)
 
 set(BLT_TARGET BLT)
 

include/blt/iterator/common.h

@@ -21,10 +21,7 @@
 
 #include <type_traits>
 #include <iterator>
-#include <blt/std/types.h>
-#include <blt/iterator/fwddecl.h>
 #include <blt/meta/meta.h>
-#include <blt/meta/iterator.h>
 
 namespace blt::iterator
 {
@@ -40,7 +37,10 @@ namespace blt::iterator
         
         base_wrapper operator--(int)
         {
-            static_assert(meta::is_bidirectional_or_better_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::bidirectional_iterator_tag> ||
+                          std::is_same_v<typename Derived::iterator_category,
+                                  std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             auto tmp = *this;
             --*this;
             return tmp;
@@ -48,7 +48,8 @@ namespace blt::iterator
         
         auto operator[](blt::ptrdiff_t n) const
         {
-            static_assert(meta::is_random_access_iterator_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             return *(*this + n);
         }
         
@@ -59,25 +60,29 @@ namespace blt::iterator
         
         friend bool operator<(const base_wrapper& a, const base_wrapper& b)
         {
-            static_assert(meta::is_random_access_iterator_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             return b - a > 0;
         }
         
         friend bool operator>(const base_wrapper& a, const base_wrapper& b)
         {
-            static_assert(meta::is_random_access_iterator_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             return b < a;
         }
         
         friend bool operator>=(const base_wrapper& a, base_wrapper& b)
         {
-            static_assert(meta::is_random_access_iterator_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             return !(a < b); // NOLINT
         }
         
         friend bool operator<=(const base_wrapper& a, const base_wrapper& b)
         {
-            static_assert(meta::is_random_access_iterator_category_v<typename Derived::iterator_category>, "Iterator must allow random access");
+            static_assert(std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>,
+                          "Iterator must allow random access");
             return !(a > b); // NOLINT
         }
         
@@ -122,28 +127,6 @@ namespace blt::iterator
         {
             return *this->iter;
         }
-
-//        zip_wrapper& operator++()
-//        {
-//            return *this;
-//        }
-//
-//        zip_wrapper& operator--()
-//        {
-//            return *this;
-//        }
-//
-//        friend zip_wrapper operator+(const zip_wrapper& a, blt::ptrdiff_t n)
-//        {
-//            static_assert(std::is_same_v<iterator_category, std::random_access_iterator_tag>,
-//                          "Iterator must allow random access");
-//        }
-//
-//        friend zip_wrapper operator-(const zip_wrapper& a, blt::ptrdiff_t n)
-//        {
-//            static_assert(std::is_same_v<iterator_category, std::random_access_iterator_tag>,
-//                          "Iterator must allow random access");
-//        }
     };
     
     namespace impl
@@ -159,17 +142,8 @@ namespace blt::iterator
                     auto begin = d->begin();
                     auto end = d->end();
                     
-                    if constexpr (meta::is_random_access_iterator_category_v<typename Derived::iterator_category>)
+                    if constexpr (std::is_same_v<typename Derived::iterator_category, std::forward_iterator_tag> ||
-                    {
+                                  std::is_same_v<typename Derived::iterator_category, std::bidirectional_iterator_tag>)
-                        // random access iterators can have math directly applied to them.
-                        if constexpr (check)
-                        {
-                            return Derived{begin + std::min(static_cast<blt::ptrdiff_t>(n), std::distance(begin, end)), end};
-                        } else
-                        {
-                            return Derived{begin + n, end};
-                        }
-                    } else
                     {
                         for (blt::size_t i = 0; i < n; i++)
                         {
@@ -181,6 +155,16 @@ namespace blt::iterator
                             ++begin;
                         }
                         return Derived{std::move(begin), std::move(end)};
+                    } else if constexpr (std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>)
+                    {
+                        // random access iterators can have math directly applied to them.
+                        if constexpr (check)
+                        {
+                            return Derived{begin + std::min(static_cast<blt::ptrdiff_t>(n), std::distance(begin, end)), end};
+                        } else
+                        {
+                            return Derived{begin + n, end};
+                        }
                     }
                 }
             
@@ -199,15 +183,15 @@ namespace blt::iterator
                 template<bool check>
                 auto take_base(blt::size_t n)
                 {
-                    static_assert(!meta::is_input_iterator_category_v<typename Derived::iterator_category>,
+                    static_assert(!std::is_same_v<typename Derived::iterator_category, std::input_iterator_tag>,
                                   "Cannot .take() on an input iterator!");
                     auto* d = static_cast<Derived*>(this);
                     auto begin = d->begin();
                     auto end = d->end();
                     
                     // take variant for forward and bidirectional iterators
-                    if constexpr (meta::is_forward_iterator_category_v<typename Derived::iterator_category> ||
+                    if constexpr (std::is_same_v<typename Derived::iterator_category, std::forward_iterator_tag> ||
-                                  meta::is_bidirectional_iterator_category_v<typename Derived::iterator_category>)
+                                  std::is_same_v<typename Derived::iterator_category, std::bidirectional_iterator_tag>)
                     {
                         // with these guys we have to loop forward to move the iterators. an unfortunate inefficiency
                         auto new_end = begin;
@@ -221,7 +205,7 @@ namespace blt::iterator
                             ++new_end;
                         }
                         return Derived{std::move(begin), std::move(new_end)};
-                    } else if constexpr (meta::is_random_access_iterator_category_v<typename Derived::iterator_category>)
+                    } else if constexpr (std::is_same_v<typename Derived::iterator_category, std::random_access_iterator_tag>)
                     {
                         // random access iterators can have math directly applied to them.
                         if constexpr (check)
@@ -248,7 +232,7 @@ namespace blt::iterator
                                public impl::skip_t<iterator_container<IterBase>>
     {
         public:
-            using iterator_category = typename std::iterator_traits<IterBase>::iterator_category;
+            using iterator_category = typename IterBase::iterator_category;
             using iterator = IterBase;
             
             iterator_container(IterBase begin, IterBase end): m_begin(std::move(begin)), m_end(std::move(end))
@@ -258,39 +242,15 @@ namespace blt::iterator
             iterator_container(Iter&& begin, Iter&& end): m_begin(std::forward<Iter>(begin)), m_end(std::forward<Iter>(end))
             {}
             
-            auto rev() const
+            auto rev()
             {
-                static_assert(meta::is_bidirectional_or_better_category_v<iterator_category>,
+                static_assert((std::is_same_v<typename IterBase::iterator_category, std::bidirectional_iterator_tag> ||
+                               std::is_same_v<typename IterBase::iterator_category, std::random_access_iterator_tag>),
                               ".rev() must be used with bidirectional (or better) iterators!");
                 return iterator_container<std::reverse_iterator<IterBase>>{std::reverse_iterator<IterBase>{end()},
                                                                            std::reverse_iterator<IterBase>{begin()}};
             }
             
-            template<typename... Iter>
-            auto zip(iterator_pair<Iter>... iterator_pairs) const
-            {
-                return zip_iterator_container(iterator_pair<decltype(begin())>{begin(), end()}, iterator_pairs...);
-            }
-            
-            template<typename... Container>
-            auto zip(Container& ... containers) const
-            {
-                return zip_iterator_container(iterator_pair<decltype(begin())>{begin(), end()},
-                                              iterator_pair{containers.begin(), containers.end()}...);
-            }
-            
-            template<typename... Container>
-            auto zip(const Container& ... containers) const
-            {
-                return zip_iterator_container(iterator_pair<decltype(begin())>{begin(), end()},
-                                              iterator_pair{containers.begin(), containers.end()}...);
-            }
-            
-            auto enumerate() const
-            {
-                return enumerate_iterator_container{begin(), end(), static_cast<blt::size_t>(std::distance(begin(), end()))};
-            }
-            
             auto begin() const
             {
                 return m_begin;

include/blt/iterator/enumerate.h

@@ -20,6 +20,7 @@
 #define BLT_ITERATOR_ENUMERATE_H
 
 #include <blt/iterator/common.h>
+#include <blt/meta/meta.h>
 #include <tuple>
 
 namespace blt
@@ -42,110 +43,17 @@ namespace blt
         class enumerate_wrapper : public passthrough_wrapper<Iter, enumerate_wrapper<Iter>>
         {
             public:
-                enumerate_wrapper(blt::size_t index, Iter iter): passthrough_wrapper<Iter, enumerate_wrapper<Iter>>(std::move(iter)), index(index)
+                using passthrough_wrapper<Iter, enumerate_wrapper<Iter>>::passthrough_wrapper;
-                {}
-                
-                using iterator_category = typename std::iterator_traits<Iter>::iterator_category;
-                using value_type = enumerate_item<meta::deref_return_t<Iter>>;
-                using difference_type = blt::ptrdiff_t;
-                using pointer = value_type;
-                using reference = value_type;
                 
                 enumerate_item<meta::deref_return_t<Iter>> operator*() const
                 {
-                    return {index, *this->iter};
+                    return *this->iter;
                 }
-                
-                enumerate_wrapper& operator++()
-                {
-                    ++index;
-                    ++this->iter;
-                    return *this;
-                }
-                
-                enumerate_wrapper& operator--()
-                {
-                    --index;
-                    --this->iter;
-                    return *this;
-                }
-                
-                friend enumerate_wrapper operator+(const enumerate_wrapper& a, blt::ptrdiff_t n)
-                {
-                    static_assert(meta::is_random_access_iterator_v<Iter>, "Iterator must allow random access");
-                    auto copy = a;
-                    copy.index += n;
-                    copy.iter = copy.iter + n;
-                    return copy;
-                }
-                
-                friend enumerate_wrapper operator-(const enumerate_wrapper& a, blt::ptrdiff_t n)
-                {
-                    static_assert(meta::is_random_access_iterator_v<Iter>, "Iterator must allow random access");
-                    auto copy = a;
-                    copy.index -= n;
-                    copy.iter = copy.iter - n;
-                    return copy;
-                }
-            
             private:
                 blt::size_t index;
         };
     }
     
-    template<typename Iter>
-    class enumerate_iterator_container : public iterator::iterator_container<iterator::enumerate_wrapper<Iter>>
-    {
-        public:
-            using iterator::iterator_container<iterator::enumerate_wrapper<Iter>>::iterator_container;
-            
-            enumerate_iterator_container(Iter begin, Iter end, blt::size_t size):
-                    iterator::iterator_container<iterator::enumerate_wrapper<Iter>>(
-                            iterator::enumerate_wrapper<Iter>{0, std::move(begin)}, iterator::enumerate_wrapper<Iter>{size, std::move(end)})
-            {}
-    };
-    
-    template<typename Iter>
-    enumerate_iterator_container(Iter, Iter, blt::size_t) -> enumerate_iterator_container<Iter>;
-    
-    namespace iterator::impl
-    {
-        template<typename Derived>
-        class enumerate_t
-        {
-            public:
-                auto enumerate()
-                {
-                    auto* d = static_cast<Derived*>(this);
-                    return enumerate_iterator_container{d->begin(), d->end(), static_cast<blt::size_t>(std::distance(d->begin(), d->end()))};
-                }
-        };
-    }
-    
-    template<typename T>
-    static inline auto enumerate(T& container)
-    {
-        return enumerate_iterator_container{container.begin(), container.end(), container.size()};
-    }
-    
-    template<typename T>
-    static inline auto enumerate(const T& container)
-    {
-        return enumerate_iterator_container{container.begin(), container.end(), container.size()};
-    }
-    
-    template<typename T, blt::size_t size>
-    static inline auto enumerate(const T(& container)[size])
-    {
-        return enumerate_iterator_container{&container[0], &container[size], size};
-    }
-    
-    template<typename T, blt::size_t size>
-    static inline auto enumerate(T(& container)[size])
-    {
-        return enumerate_iterator_container{&container[0], &container[size], size};
-    }
-    
 }
 
 #endif //BLT_ITERATOR_ENUMERATE_H

include/blt/iterator/fwddecl.h

@@ -1,61 +0,0 @@
-#pragma once
-/*
- *  Copyright (C) 2024  Brett Terpstra
- *
- *  This program is free software: you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation, either version 3 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-#ifndef BLT_ITERATOR_FWDDECL_H
-#define BLT_ITERATOR_FWDDECL_H
-
-namespace blt
-{
-    template<typename... Iter>
-    class zip_iterator_container;
-    
-    template<typename Iter>
-    class enumerate_iterator_container;
-    
-    namespace iterator
-    {
-        template<typename Iter>
-        struct iterator_pair;
-        
-        template<typename T>
-        struct enumerate_item;
-        
-        template<typename Iter>
-        class enumerate_wrapper;
-        
-        template<typename... Iter>
-        struct zip_wrapper;
-        
-        namespace impl
-        {
-            template<typename Derived>
-            class skip_t;
-            
-            template<typename Derived>
-            class take_t;
-            
-            template<typename Derived>
-            class zip_t;
-            
-            template<typename Derived>
-            class enumerate_t;
-        }
-    }
-}
-
-#endif //BLT_ITERATOR_FWDDECL_H

include/blt/iterator/iterator.h

@@ -19,9 +19,12 @@
 #ifndef BLT_ITERATOR_H
 #define BLT_ITERATOR_H
 
+#include <blt/std/types.h>
+#include <blt/std/logging.h>
 #include <blt/iterator/common.h>
 #include <blt/iterator/zip.h>
-#include <blt/iterator/enumerate.h>
+#include <blt/meta/meta.h>
+#include <blt/meta/iterator.h>
 #include <type_traits>
 #include <iterator>
 #include <tuple>
@@ -29,28 +32,721 @@
 namespace blt
 {
     
-    template<typename T>
+    // forward declare useful types
-    static inline auto iterate(T& container)
+    template<typename Iter, typename = std::void_t<>>
+    class enumerator;
+    
+    template<typename Iter, typename = std::void_t<>>
+    class enumerator_rev;
+    
+    template<typename Iter1, typename Iter2, typename = std::void_t<>>
+    class pair_iterator;
+    
+    template<typename Iter, typename Iter2, typename = std::void_t<>>
+    class pair_iterator_rev;
+    
+    template<typename... Iter>
+    class zip_iterator;
+    
+    template<typename... Iter>
+    class zip_iterator_rev;
+    
+    namespace iterator
     {
-        return iterator::iterator_container<decltype(container.begin())>{container.begin(), container.end()};
+        template<typename Iter, typename = std::void_t<>>
+        class enumerate_wrapper;
+        
+        template<typename Iter1, typename Iter2, typename = std::void_t<>>
+        class pair_wrapper;
+        
+        /**
+         * struct which is returned by the enumerator.
+         * @tparam T type to store.
+         */
+        template<typename T>
+        struct enumerate_item
+        {
+            blt::size_t index;
+            T value;
+        };
+        
+        /**
+         * base class for iterators which operate on pairs of values. Handles comparison.
+         * @tparam Iter1 first iterator type. this will be used for comparison.
+         * @tparam Iter2 second iterator type. this value is not modified by this class.
+         */
+        template<typename Iter1, typename Iter2>
+        class dual_iterator_base
+        {
+            public:
+                explicit dual_iterator_base(Iter1 iter1, Iter2 iter2): m_iter1(std::move(iter1)), m_iter2(std::move(iter2))
+                {}
+                
+                friend bool operator==(const dual_iterator_base& a, const dual_iterator_base& b)
+                {
+                    return a.m_iter1 == b.m_iter1;
                 }
                 
-    template<typename T>
+                friend bool operator!=(const dual_iterator_base& a, const dual_iterator_base& b)
-    static inline auto iterate(const T& container)
                 {
-        return iterator::iterator_container<decltype(container.begin())>{container.begin(), container.end()};
+                    return a.m_iter1 != b.m_iter1;
+                }
+                
+                auto iter1() const
+                {
+                    return m_iter1;
+                }
+                
+                auto iter2() const
+                {
+                    return m_iter2;
+                }
+            
+            protected:
+                Iter1 m_iter1;
+                Iter2 m_iter2;
+        };
+        
+        /**
+         * Base class for all enumerator iterators. Handles the deference (*) operator.
+         * @tparam Iter iterator type
+         */
+        template<typename Iter>
+        class enumerate_iterator_base : public dual_iterator_base<Iter, blt::size_t>
+        {
+            public:
+                explicit enumerate_iterator_base(Iter iter, blt::size_t place = 0):
+                        dual_iterator_base<Iter, blt::size_t>(std::move(iter), place)
+                {}
+                
+                enumerate_item<blt::meta::deref_return_t<Iter>> operator*() const
+                {
+                    return {this->m_iter2, *this->m_iter1};
+                }
+        };
+        
+        template<typename Iter1, typename Iter2>
+        class pair_iterator_base : public dual_iterator_base<Iter1, Iter2>
+        {
+            public:
+                using dual_iterator_base<Iter1, Iter2>::dual_iterator_base;
+                
+                std::pair<blt::meta::deref_return_t<Iter1>, blt::meta::deref_return_t<Iter2>> operator*() const
+                {
+                    return {*this->m_iter1, *this->m_iter2};
+                }
+        };
+        
+        /**
+         * Forward iterator base class. Contains the ++ operator.
+         * @tparam Base iterator base type.
+         */
+        template<typename Base>
+        class forward_iterator_base : public Base
+        {
+            public:
+                using Base::Base;
+                
+                forward_iterator_base& operator++()
+                {
+                    ++this->m_iter1;
+                    ++this->m_iter2;
+                    return *this;
+                }
+                
+                forward_iterator_base operator++(int)
+                {
+                    auto tmp = *this;
+                    ++*this;
+                    return tmp;
+                }
+        };
+        
+        /**
+         * Bidirectional iterator base class. Contains the -- operator.
+         * @tparam Base iterator base type.
+         */
+        template<typename Base>
+        class bidirectional_iterator_base : public Base
+        {
+            public:
+                using Base::Base;
+                
+                bidirectional_iterator_base& operator--()
+                {
+                    --this->m_iter1;
+                    --this->m_iter2;
+                    return *this;
+                }
+                
+                bidirectional_iterator_base operator--(int)
+                {
+                    auto tmp = *this;
+                    --*this;
+                    return tmp;
+                }
+        };
+        
+        template<typename Iter>
+        using enumerate_forward_iterator = forward_iterator_base<enumerate_iterator_base<Iter>>;
+        
+        template<typename Iter>
+        using enumerate_bidirectional_iterator = bidirectional_iterator_base<enumerate_forward_iterator<Iter>>;
+        
+        template<typename Iter1, typename Iter2>
+        using pair_forward_iterator = forward_iterator_base<pair_iterator_base<Iter1, Iter2>>;
+        
+        template<typename Iter1, typename Iter2>
+        using pair_bidirectional_iterator = bidirectional_iterator_base<pair_forward_iterator<Iter1, Iter2>>;
+        
+        /**
+         * Enumerator wrapper class specialization for forward iterators.
+         * @tparam Iter iterator type
+         */
+        template<typename Iter>
+        class enumerate_wrapper<Iter, std::enable_if_t<blt::meta::is_forward_iterator_v<Iter>, std::void_t<std::forward_iterator_tag>>>
+                : public enumerate_forward_iterator<Iter>
+        {
+            public:
+                using iterator_category = std::forward_iterator_tag;
+                using value_type = enumerate_item<blt::meta::deref_return_t<Iter>>;
+                using difference_type = typename std::iterator_traits<Iter>::difference_type;
+                using pointer = value_type;
+                using reference = value_type;
+                
+                using enumerate_forward_iterator<Iter>::enumerate_forward_iterator;
+        };
+        
+        /**
+         * Pair wrapper class specialization for forward iterators.
+         * @tparam Iter iterator type
+         */
+        template<typename Iter1, typename Iter2>
+        class pair_wrapper<Iter1, Iter2, std::enable_if_t<
+                blt::meta::is_forward_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                std::void_t<std::forward_iterator_tag>>> : public pair_forward_iterator<Iter1, Iter2>
+        {
+            public:
+                using iterator_category = std::forward_iterator_tag;
+                using value_type = std::pair<blt::meta::deref_return_t<Iter1>, blt::meta::deref_return_t<Iter2>>;
+                using difference_type = std::common_type_t<typename std::iterator_traits<Iter1>::difference_type, typename std::iterator_traits<Iter2>::difference_type>;
+                using pointer = value_type;
+                using reference = value_type;
+                
+                using pair_forward_iterator<Iter1, Iter2>::pair_forward_iterator;
+        };
+        
+        /**
+         * Enumerator wrapper class for bidirectional iterators or random access iterators.
+         * @tparam Iter iterator type.
+         */
+        template<typename Iter>
+        class enumerate_wrapper<Iter, std::enable_if_t<blt::meta::is_bidirectional_or_better_v<Iter>, std::void_t<std::bidirectional_iterator_tag>>>
+                : public enumerate_bidirectional_iterator<Iter>
+        {
+            public:
+                using iterator_category = std::bidirectional_iterator_tag;
+                using value_type = enumerate_item<blt::meta::deref_return_t<Iter>>;
+                using difference_type = typename std::iterator_traits<Iter>::difference_type;
+                using pointer = value_type;
+                using reference = value_type;
+                
+                using enumerate_bidirectional_iterator<Iter>::enumerate_bidirectional_iterator;
+        };
+        
+        /**
+         * Pair wrapper class for bidirectional iterators or random access iterators.
+         * @tparam Iter iterator type.
+         */
+        template<typename Iter1, typename Iter2>
+        class pair_wrapper<Iter1, Iter2, std::enable_if_t<
+                blt::meta::is_bidirectional_or_better_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                std::void_t<std::bidirectional_iterator_tag>>> : public pair_bidirectional_iterator<Iter1, Iter2>
+        {
+            public:
+                using iterator_category = std::bidirectional_iterator_tag;
+                using value_type = std::pair<blt::meta::deref_return_t<Iter1>, blt::meta::deref_return_t<Iter2>>;
+                using difference_type = std::common_type_t<typename std::iterator_traits<Iter1>::difference_type, typename std::iterator_traits<Iter2>::difference_type>;
+                using pointer = value_type;
+                using reference = value_type;
+                
+                using pair_bidirectional_iterator<Iter1, Iter2>::pair_bidirectional_iterator;
+        };
+        
+        /**
+         * Base class for storing begin/end iterators.
+         * @tparam IterWrapper wrapper used to iterate
+         * @tparam CompleteClass completed class returned from skip/take methods
+         */
+        template<typename IterWrapper, typename CompleteClass>
+        class iterator_storage_base
+        {
+            public:
+                explicit iterator_storage_base(IterWrapper begin, IterWrapper end): begin_(std::move(begin)), end_(std::move(end))
+                {}
+                
+                auto begin()
+                {
+                    return begin_;
+                }
+                
+                auto end()
+                {
+                    return end_;
+                }
+                
+                /**
+                 * Creates an enumerator that skips the first n elements.
+                 * @param amount amount of values to skip.
+                 */
+                auto skip(blt::size_t amount)
+                {
+                    auto begin = this->begin_;
+                    for (blt::size_t i = 0; i < amount; i++)
+                        ++begin;
+                    return CompleteClass{begin.iter1(),
+                                         this->end_.iter1(),
+                                         begin.iter2(),
+                                         this->end_.iter2()};
+                }
+                
+                /**
+                 * Creates an enumerator that yields the first n elements, or UB if the underlying iterator ends sooner.
+                 * @param amount amount to take.
+                 */
+                auto take(blt::size_t amount)
+                {
+                    auto end = this->begin();
+                    for (blt::size_t i = 0; i < amount; i++)
+                        ++end;
+                    return CompleteClass{this->begin_.iter1(),
+                                         end.iter1(),
+                                         this->begin_.iter2(),
+                                         end.iter2()};
+                }
+            
+            protected:
+                IterWrapper begin_;
+                IterWrapper end_;
+        };
+        
+        /**
+         * Reversible (bidirectional) base class storing the begin / end iterators.
+         * @tparam Iter iterator type.
+         * @tparam IterWrapper wrapper used to iterate.
+         * @tparam CompleteClass completed class returned from skip/take methods
+         * @tparam CompleteClassRev reverse version of CompleteClass, returned from rev
+         */
+        template<typename IterWrapper, typename CompleteClass, typename CompleteClassRev>
+        class iterator_storage_reversible : public iterator_storage_base<IterWrapper, CompleteClass>
+        {
+            public:
+                explicit iterator_storage_reversible(IterWrapper begin, IterWrapper end):
+                        iterator_storage_base<IterWrapper, CompleteClass>{std::move(begin), std::move(end)}
+                {}
+                
+                /**
+                 * Reverses the enumerator’s direction.
+                 */
+                auto rev() const
+                {
+                    return CompleteClassRev{this->end_.iter1(),
+                                            this->begin_.iter1(),
+                                            this->end_.iter2(),
+                                            this->begin_.iter2()};
+                }
+        };
+        
+        /**
+         * Random access base class storage for begin/end iterators.
+         * Has updated skip and take methods which make use of the random access nature of the iterator.
+         * @tparam Iter iterator type.
+         * @tparam IterWrapper wrapper used to iterate.
+         * @tparam CompleteClass completed class returned from skip/take methods
+         * @tparam CompleteClassRev reverse version of CompleteClass, returned from rev
+         */
+        template<typename IterWrapper, typename CompleteClass, typename CompleteClassRev>
+        class iterator_storage_random_access : public iterator_storage_reversible<IterWrapper, CompleteClass, CompleteClassRev>
+        {
+            public:
+                using iterator_storage_reversible<IterWrapper, CompleteClass, CompleteClassRev>::iterator_storage_reversible;
+                
+                auto skip(blt::size_t amount)
+                {
+                    return CompleteClass{this->begin_.iter1() + amount,
+                                         this->end_.iter1(),
+                                         this->begin_.iter2() + amount,
+                                         this->end_.iter2()};
+                }
+                
+                auto take(blt::size_t amount)
+                {
+                    return CompleteClass{this->begin_.iter1(),
+                                         this->begin_.iter1() + amount,
+                                         this->begin_.iter2(),
+                                         this->begin_.iter2() + amount};
+                }
+        };
+        
+        /**
+         * Reversible (bidirectional) base class for storing the begin/end iterators, operates in reverse for reverse iteration.
+         * @tparam Iter iterator type.
+         * @tparam IterWrapper wrapper used to iterate (std::reverse_iterator<enumerate_wrapper>).
+         * @tparam CompleteClass completed class returned from skip/take methods
+         * @tparam CompleteClassRev reverse version of CompleteClass, returned from rev
+         */
+        template<typename IterWrapper, typename CompleteClass, typename CompleteClassRev>
+        class iterator_storage_reversible_rev : public iterator_storage_reversible<IterWrapper, CompleteClass, CompleteClassRev>
+        {
+            public:
+                using iterator_storage_reversible<IterWrapper, CompleteClass, CompleteClassRev>::iterator_storage_reversible;
+                
+                auto rev() const
+                {
+                    return CompleteClass{this->end_.base().iter1(),
+                                         this->begin_.base().iter1(),
+                                         this->end_.base().iter2(),
+                                         this->begin_.base().iter2()};
+                }
+                
+                auto skip(blt::size_t amount)
+                {
+                    auto begin = this->begin_.base();
+                    for (blt::size_t i = 0; i < amount; i++)
+                        --begin;
+                    return CompleteClassRev{begin.iter1(),
+                                            this->end_.base().iter1(),
+                                            begin.iter2(),
+                                            this->end_.base().iter2()};
+                }
+                
+                auto take(blt::size_t amount)
+                {
+                    auto end = this->begin_.base();
+                    for (blt::size_t i = 0; i < amount; i++)
+                        --end;
+                    return CompleteClassRev{
+                            this->begin_.base().iter1(),
+                            end.iter1(),
+                            this->begin_.base().iter2(),
+                            end.iter2()};
+                }
+        };
+        
+        /**
+         * Random access base class for storing the begin/end iterator.
+         * Has updated skip and take methods which make use of the random access nature of the iterator.
+         * Operates in reverse for reverse iteration.
+         * @tparam Iter iterator type.
+         * @tparam IterWrapper wrapper used to iterate (std::reverse_iterator<enumerate_wrapper>).
+         * @tparam CompleteClass completed class returned from skip/take methods
+         * @tparam CompleteClassRev reverse version of CompleteClass, returned from rev
+         */
+        template<typename IterWrapper, typename CompleteClass, typename CompleteClassRev>
+        class iterator_storage_random_access_rev : public iterator_storage_reversible_rev<IterWrapper, CompleteClass, CompleteClassRev>
+        {
+            public:
+                using iterator_storage_reversible_rev<IterWrapper, CompleteClass, CompleteClassRev>::iterator_storage_reversible_rev;
+                
+                auto skip(blt::size_t amount)
+                {
+                    return CompleteClassRev{this->begin_.base().iter1() - amount,
+                                            this->end_.base().iter1(),
+                                            this->begin_.base().iter2() - amount,
+                                            this->end_.base().iter2()};
+                }
+                
+                auto take(blt::size_t amount)
+                {
+                    return CompleteClassRev{this->begin_.base().iter1(),
+                                            this->begin_.base().iter1() - amount,
+                                            this->begin_.base().iter2(),
+                                            this->begin_.base().iter2() - amount};
+                }
+        };
+        
+        /**
+         * Base class for types which can be converted to an enumerator
+         */
+        template<typename Derived, typename CompleteEnumerator>
+        class enumerator_convertible
+        {
+            public:
+                auto enumerate()
+                {
+                    auto* b = static_cast<Derived*>(this);
+                    return CompleteEnumerator{b->begin(), b->end(), static_cast<blt::size_t>(std::distance(b->begin(), b->end()))};
+                }
+        };
+    }
+    
+    /**
+     * Enumerator specialization for forward iterators
+     */
+    template<typename Iter>
+    class enumerator<Iter, std::enable_if_t<blt::meta::is_forward_iterator_v<Iter>, std::void_t<std::forward_iterator_tag>>>
+            : public iterator::iterator_storage_base<iterator::enumerate_wrapper<Iter>, enumerator<Iter>>
+    {
+        public:
+            explicit enumerator(Iter begin, Iter end, blt::size_t container_size):
+                    iterator::iterator_storage_base<iterator::enumerate_wrapper<Iter>, enumerator<Iter>>
+                            {iterator::enumerate_wrapper<Iter>{std::move(begin), 0},
+                             iterator::enumerate_wrapper<Iter>{std::move(end), container_size}}
+            {}
+            
+            explicit enumerator(Iter begin, Iter end, blt::size_t begin_index, blt::size_t end_index):
+                    iterator::iterator_storage_base<iterator::enumerate_wrapper<Iter>, enumerator<Iter>>{
+                            iterator::enumerate_wrapper<Iter>{std::move(begin), begin_index},
+                            iterator::enumerate_wrapper<Iter>{std::move(end), end_index}}
+            {}
+    };
+    
+    /**
+     * Enumerator specialization for bidirectional iterators
+     */
+    template<typename Iter>
+    class enumerator<Iter, std::enable_if_t<blt::meta::is_bidirectional_iterator_v<Iter>, std::void_t<std::bidirectional_iterator_tag>>>
+            : public iterator::iterator_storage_reversible<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>
+    {
+        public:
+            explicit enumerator(Iter begin, Iter end, blt::size_t container_size):
+                    iterator::iterator_storage_reversible<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>
+                            {iterator::enumerate_wrapper<Iter>{std::move(begin), 0},
+                             iterator::enumerate_wrapper<Iter>{std::move(end), container_size}}
+            {}
+            
+            explicit enumerator(Iter begin, Iter end, blt::size_t begin_index, blt::size_t end_index):
+                    iterator::iterator_storage_reversible<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>{
+                            iterator::enumerate_wrapper<Iter>{std::move(begin), begin_index},
+                            iterator::enumerate_wrapper<Iter>{std::move(end), end_index}}
+            {}
+    };
+    
+    /**
+     * Enumerator specialization for random access iterators
+     */
+    template<typename Iter>
+    class enumerator<Iter, std::enable_if_t<blt::meta::is_random_access_iterator_v<Iter>, std::void_t<std::random_access_iterator_tag>>>
+            : public iterator::iterator_storage_random_access<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>
+    {
+        public:
+            explicit enumerator(Iter begin, Iter end, blt::size_t container_size):
+                    iterator::iterator_storage_random_access<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>
+                            {iterator::enumerate_wrapper<Iter>{std::move(begin), 0},
+                             iterator::enumerate_wrapper<Iter>{std::move(end), container_size}}
+            {}
+            
+            explicit enumerator(Iter begin, Iter end, blt::size_t begin_index, blt::size_t end_index):
+                    iterator::iterator_storage_random_access<iterator::enumerate_wrapper<Iter>, enumerator<Iter>, enumerator_rev<Iter>>{
+                            iterator::enumerate_wrapper<Iter>{std::move(begin), begin_index},
+                            iterator::enumerate_wrapper<Iter>{std::move(end), end_index}}
+            {}
+    };
+    
+    /**
+     * Reverse enumerator specialization for bidirectional iterators
+     */
+    template<typename Iter>
+    class enumerator_rev<Iter, std::enable_if_t<blt::meta::is_bidirectional_iterator_v<Iter>, std::void_t<std::bidirectional_iterator_tag>>>
+            : public iterator::iterator_storage_reversible_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>
+    {
+        public:
+            explicit enumerator_rev(Iter begin, Iter end, blt::size_t container_size):
+                    iterator::iterator_storage_reversible_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>
+                            {std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{iterator::enumerate_wrapper<Iter>{std::move(begin), 0}},
+                             std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{
+                                     iterator::enumerate_wrapper<Iter>{std::move(end), container_size}}}
+            {}
+            
+            explicit enumerator_rev(Iter begin, Iter end, blt::size_t begin_index, blt::size_t end_index):
+                    iterator::iterator_storage_reversible_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>{
+                            std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{
+                                    iterator::enumerate_wrapper<Iter>{std::move(begin), begin_index}},
+                            std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{iterator::enumerate_wrapper<Iter>{std::move(end), end_index}}}
+            {}
+    };
+    
+    /**
+     * Reverse enumerator specialization for random access iterators
+     */
+    template<typename Iter>
+    class enumerator_rev<Iter, std::enable_if_t<blt::meta::is_random_access_iterator_v<Iter>, std::void_t<std::random_access_iterator_tag>>>
+            : public iterator::iterator_storage_random_access_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>
+    {
+        public:
+            explicit enumerator_rev(Iter begin, Iter end, blt::size_t container_size):
+                    iterator::iterator_storage_random_access_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>
+                            {std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{iterator::enumerate_wrapper<Iter>{std::move(begin), 0}},
+                             std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{
+                                     iterator::enumerate_wrapper<Iter>{std::move(end), container_size}}}
+            {}
+            
+            explicit enumerator_rev(Iter begin, Iter end, blt::size_t begin_index, blt::size_t end_index):
+                    iterator::iterator_storage_random_access_rev<std::reverse_iterator<iterator::enumerate_wrapper<Iter>>, enumerator<Iter>, enumerator_rev<Iter>>{
+                            std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{
+                                    iterator::enumerate_wrapper<Iter>{std::move(begin), begin_index}},
+                            std::reverse_iterator<iterator::enumerate_wrapper<Iter>>{iterator::enumerate_wrapper<Iter>{std::move(end), end_index}}}
+            {}
+    };
+    
+    // CTAD for enumerators
+    
+    template<typename Iter>
+    enumerator(Iter, Iter) -> enumerator<Iter>;
+    
+    template<typename Iter>
+    enumerator(Iter, Iter, blt::size_t) -> enumerator<Iter>;
+    
+    template<typename Iter>
+    enumerator(Iter, Iter, blt::size_t, blt::size_t) -> enumerator<Iter>;
+    
+    template<typename Iter1, typename Iter2>
+    class pair_iterator<Iter1, Iter2,
+            std::enable_if_t<
+                    blt::meta::is_forward_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                    std::void_t<std::forward_iterator_tag>>>
+            : public iterator::iterator_storage_base<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>>,
+              public iterator::enumerator_convertible<pair_iterator<Iter1, Iter2>, enumerator<iterator::pair_wrapper<Iter1, Iter2>>>
+    {
+        public:
+            explicit pair_iterator(Iter1 begin1, Iter1 end1, Iter2 begin2, Iter2 end2):
+                    iterator::iterator_storage_base<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>>
+                            {iterator::pair_wrapper<Iter1, Iter2>{std::move(begin1), std::move(begin2)},
+                             iterator::pair_wrapper<Iter1, Iter2>{std::move(end1), std::move(end2)}}
+            {}
+    };
+    
+    template<typename Iter1, typename Iter2>
+    class pair_iterator<Iter1, Iter2,
+            std::enable_if_t<
+                    blt::meta::is_bidirectional_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                    std::void_t<std::bidirectional_iterator_tag>>>
+            : public iterator::iterator_storage_reversible<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>,
+              public iterator::enumerator_convertible<pair_iterator<Iter1, Iter2>, enumerator<iterator::pair_wrapper<Iter1, Iter2>>>
+    {
+        public:
+            explicit pair_iterator(Iter1 begin1, Iter1 end1, Iter2 begin2, Iter2 end2):
+                    iterator::iterator_storage_reversible<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>
+                            {iterator::pair_wrapper<Iter1, Iter2>{std::move(begin1), std::move(begin2)},
+                             iterator::pair_wrapper<Iter1, Iter2>{std::move(end1), std::move(end2)}}
+            {}
+    };
+    
+    template<typename Iter1, typename Iter2>
+    class pair_iterator<Iter1, Iter2,
+            std::enable_if_t<
+                    blt::meta::is_random_access_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                    std::void_t<std::random_access_iterator_tag>>>
+            : public iterator::iterator_storage_random_access<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>,
+              public iterator::enumerator_convertible<pair_iterator<Iter1, Iter2>, enumerator<iterator::pair_wrapper<Iter1, Iter2>>>
+    {
+        public:
+            explicit pair_iterator(Iter1 begin1, Iter1 end1, Iter2 begin2, Iter2 end2):
+                    iterator::iterator_storage_random_access<iterator::pair_wrapper<Iter1, Iter2>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>
+                            {iterator::pair_wrapper<Iter1, Iter2>{std::move(begin1), std::move(begin2)},
+                             iterator::pair_wrapper<Iter1, Iter2>{std::move(end1), std::move(end2)}}
+            {}
+    };
+    
+    template<typename Iter1, typename Iter2>
+    class pair_iterator_rev<Iter1, Iter2,
+            std::enable_if_t<
+                    blt::meta::is_bidirectional_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                    std::void_t<std::bidirectional_iterator_tag>>>
+            : public iterator::iterator_storage_reversible_rev<std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>,
+              public iterator::enumerator_convertible<pair_iterator<Iter1, Iter2>, enumerator<iterator::pair_wrapper<Iter1, Iter2>>>
+    {
+        public:
+            explicit pair_iterator_rev(Iter1 begin1, Iter1 end1, Iter2 begin2, Iter2 end2):
+                    iterator::iterator_storage_reversible_rev<std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>
+                            {std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>{
+                                    iterator::pair_wrapper<Iter1, Iter2>{std::move(begin1), std::move(begin2)}},
+                             std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>{
+                                     iterator::pair_wrapper<Iter1, Iter2>{std::move(end1), std::move(end2)}}}
+            {}
+    };
+    
+    template<typename Iter1, typename Iter2>
+    class pair_iterator_rev<Iter1, Iter2,
+            std::enable_if_t<
+                    blt::meta::is_random_access_iterator_category_v<blt::meta::lowest_iterator_category_t<Iter1, Iter2>>,
+                    std::void_t<std::random_access_iterator_tag>>>
+            : public iterator::iterator_storage_random_access_rev<std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>,
+              public iterator::enumerator_convertible<pair_iterator<Iter1, Iter2>, enumerator<iterator::pair_wrapper<Iter1, Iter2>>>
+    {
+        public:
+            explicit pair_iterator_rev(Iter1 begin1, Iter1 end1, Iter2 begin2, Iter2 end2):
+                    iterator::iterator_storage_random_access_rev<std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>, pair_iterator<Iter1, Iter2>, pair_iterator_rev<Iter1, Iter2>>
+                            {std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>{
+                                    iterator::pair_wrapper<Iter1, Iter2>{std::move(begin1), std::move(begin2)}},
+                             std::reverse_iterator<iterator::pair_wrapper<Iter1, Iter2>>{
+                                     iterator::pair_wrapper<Iter1, Iter2>{std::move(end1), std::move(end2)}}}
+            {}
+    };
+    
+    // CTAD for pair iterators
+    
+    template<typename Iter1, typename Iter2>
+    pair_iterator(Iter1, Iter1, Iter2, Iter2) -> pair_iterator<Iter1, Iter2>;
+    
+    template<typename T, blt::size_t size>
+    static inline auto enumerate(const T(& container)[size])
+    {
+        return enumerator{&container[0], &container[size], size};
     }
     
     template<typename T, blt::size_t size>
-    static inline auto iterate(const T(& container)[size])
+    static inline auto enumerate(T(& container)[size])
     {
-        return iterator::iterator_container<decltype(container.begin())>{&container[0], &container[size]};
+        return enumerator{&container[0], &container[size], size};
     }
     
-    template<typename T, blt::size_t size>
+    template<typename T>
-    static inline auto iterate(T(& container)[size])
+    static inline auto enumerate(T& container)
     {
-        return iterator::iterator_container<decltype(container.begin())>{&container[0], &container[size]};
+        return enumerator{container.begin(), container.end(), container.size()};
+    }
+    
+    template<typename T>
+    static inline auto enumerate(T&& container)
+    {
+        return enumerator{container.begin(), container.end(), container.size()};
+    }
+    
+    template<typename T>
+    static inline auto enumerate(const T& container)
+    {
+        return enumerator{container.begin(), container.end(), container.size()};
+    }
+    
+    template<typename T, typename G>
+    static inline auto in_pairs(const T& container1, const G& container2)
+    {
+        return pair_iterator{container1.begin(), container1.end(), container2.begin(), container2.end()};
+    }
+    
+    template<typename T, typename G>
+    static inline auto in_pairs(T& container1, G& container2)
+    {
+        return pair_iterator{container1.begin(), container1.end(), container2.begin(), container2.end()};
+    }
+    
+    template<typename T, typename G, blt::size_t size>
+    static inline auto in_pairs(const T(& container1)[size], const G(& container2)[size])
+    {
+        return pair_iterator{&container1[0], &container1[size], &container2[0], &container2[size]};
+    }
+    
+    template<typename T, typename G, blt::size_t size>
+    static inline auto in_pairs(T(& container1)[size], G(& container2)[size])
+    {
+        return pair_iterator{&container1[0], &container1[size], &container2[0], &container2[size]};
+    }
+    
+    template<typename T, typename G>
+    static inline auto in_pairs(T&& container1, G&& container2)
+    {
+        return pair_iterator{container1.begin(), container1.end(), container2.begin(), container2.end()};
     }
     
 }

include/blt/iterator/zip.h

@@ -20,6 +20,8 @@
 #define BLT_ITERATOR_ZIP
 
 #include <blt/iterator/common.h>
+#include <blt/meta/meta.h>
+#include <blt/meta/iterator.h>
 #include <tuple>
 
 namespace blt
@@ -55,20 +57,21 @@ namespace blt
                 
                 zip_wrapper& operator--()
                 {
-                    static_assert(meta::is_bidirectional_or_better_category_v<iterator_category>, "Iterator must be bidirectional or better!");
                     std::apply([](auto& ... i) { ((--i), ...); }, this->iter);
                     return *this;
                 }
                 
                 friend zip_wrapper operator+(const zip_wrapper& a, blt::ptrdiff_t n)
                 {
-                    static_assert(meta::is_random_access_iterator_category_v<iterator_category>, "Iterator must allow random access");
+                    static_assert(std::is_same_v<iterator_category, std::random_access_iterator_tag>,
+                                  "Iterator must allow random access");
                     return std::apply([n](auto& ... i) { return zip_wrapper((i + n)...); }, a.iter);
                 }
                 
                 friend zip_wrapper operator-(const zip_wrapper& a, blt::ptrdiff_t n)
                 {
-                    static_assert(meta::is_random_access_iterator_category_v<iterator_category>, "Iterator must allow random access");
+                    static_assert(std::is_same_v<iterator_category, std::random_access_iterator_tag>,
+                                  "Iterator must allow random access");
                     return std::apply([n](auto& ... i) { return zip_wrapper((i - n)...); }, a.iter);
                 }
                 
@@ -95,6 +98,19 @@ namespace blt
                 }
         };
 
+//        template<typename Iter>
+//        struct zip_wrapper<Iter> : public Iter
+//        {
+//            using iterator_category = typename std::iterator_traits<Iter>::iterator_category;
+//            using value_type = typename std::iterator_traits<Iter>::value_type;
+//            using difference_type = typename std::iterator_traits<Iter>::difference_type;
+//            using pointer = typename std::iterator_traits<Iter>::pointer;
+//            using reference = typename std::iterator_traits<Iter>::reference;
+//
+//            using Iter::Iter;
+//        };
+    }
+    
     template<typename Iter>
     struct iterator_pair
     {
@@ -106,7 +122,6 @@ namespace blt
         Iter begin;
         Iter end;
     };
-    }
     
     template<typename... Iter>
     class zip_iterator_container : public iterator::iterator_container<iterator::zip_wrapper<Iter...>>
@@ -114,24 +129,24 @@ namespace blt
         public:
             using iterator::iterator_container<iterator::zip_wrapper<Iter...>>::iterator_container;
             
-            explicit zip_iterator_container(iterator::iterator_pair<Iter>... iterator_pairs):
+            explicit zip_iterator_container(iterator_pair<Iter>... iterator_pairs):
                     iterator::iterator_container<iterator::zip_wrapper<Iter...>>(iterator::zip_wrapper<Iter...>{std::move(iterator_pairs.begin)...},
                                                                                  iterator::zip_wrapper<Iter...>{std::move(iterator_pairs.end)...})
             {}
         
     };
     
-    namespace iterator::impl
+    namespace impl
     {
         template<typename Derived>
         class zip_t
         {
             public:
                 template<typename... Iter>
-                auto zip(iterator::iterator_pair<Iter>... iterator_pairs)
+                auto zip(iterator_pair<Iter>... iterator_pairs)
                 {
                     auto* d = static_cast<Derived*>(this);
-                    return zip_iterator_container(iterator::iterator_pair<decltype(d->begin())>{d->begin(), d->end()}, iterator_pairs...);
+                    return zip_iterator_container(iterator_pair<decltype(d->begin())>{d->begin(), d->end()}, iterator_pairs...);
                 }
         };
     }
@@ -141,7 +156,7 @@ namespace blt
      */
     
     template<typename... Iter>
-    zip_iterator_container(iterator::iterator_pair<Iter>...) -> zip_iterator_container<Iter...>;
+    zip_iterator_container(iterator_pair<Iter>...) -> zip_iterator_container<Iter...>;
     
     template<typename... Iter>
     zip_iterator_container(std::initializer_list<Iter>...) -> zip_iterator_container<Iter...>;
@@ -154,43 +169,8 @@ namespace blt
     template<typename... Container>
     auto zip(Container& ... container)
     {
-        return zip_iterator_container{iterator::iterator_pair{std::begin(container), std::end(container)}...};
+        return zip_iterator_container{iterator_pair{container.begin(), container.end()}...};
     }
-    
-    template<typename... Container>
-    auto zip(const Container& ... container)
-    {
-        return zip_iterator_container{iterator::iterator_pair{std::begin(container), std::end(container)}...};
-    }
-    
-    template<typename T, typename G>
-    static inline auto in_pairs(const T& container1, const G& container2)
-    {
-        return zip_iterator_container{iterator::iterator_pair{container1.begin(), container1.end()},
-                                      iterator::iterator_pair{container2.begin(), container2.end()}};
-    }
-    
-    template<typename T, typename G>
-    static inline auto in_pairs(T& container1, G& container2)
-    {
-        return zip_iterator_container{iterator::iterator_pair{container1.begin(), container1.end()},
-                                      iterator::iterator_pair{container2.begin(), container2.end()}};
-    }
-    
-    template<typename T, typename G, blt::size_t size>
-    static inline auto in_pairs(const T(& container1)[size], const G(& container2)[size])
-    {
-        return zip_iterator_container{iterator::iterator_pair{&container1[0], &container1[size]},
-                                      iterator::iterator_pair{&container2[0], &container2[size]}};
-    }
-    
-    template<typename T, typename G, blt::size_t size>
-    static inline auto in_pairs(T(& container1)[size], G(& container2)[size])
-    {
-        return zip_iterator_container{iterator::iterator_pair{&container1[0], &container1[size]},
-                                      iterator::iterator_pair{&container2[0], &container2[size]}};
-    }
-    
 }
 
 #endif //BLT_ITERATOR_ZIP

include/blt/math/matrix.h

@@ -122,7 +122,7 @@ namespace blt
                 return *this;
             }
             
-            [[nodiscard]] constexpr generalized_matrix<T, columns, rows> transpose() const
+            constexpr generalized_matrix<T, columns, rows> transpose() const
             {
                 generalized_matrix<T, columns, rows> mat;
                 
@@ -135,7 +135,7 @@ namespace blt
                 return mat;
             }
             
-            [[nodiscard]] constexpr T magnitude() const
+            T magnitude() const
             {
                 T ret{};
                 for (blt::u32 i = 0; i < columns; i++)
@@ -146,7 +146,7 @@ namespace blt
                 return std::sqrt(ret);
             }
             
-            [[nodiscard]] constexpr matrix_t normalize() const
+            matrix_t normalize() const
             {
                 auto mag = magnitude();
                 matrix_t mat = *this;
@@ -155,14 +155,6 @@ namespace blt
                 return mat / mag;
             }
             
-            [[nodiscard]] constexpr matrix_t abs() const
-            {
-                matrix_t copy = *this;
-                for (auto& v : copy.data)
-                    v = v.abs();
-                return copy;
-            }
-            
             constexpr inline const blt::vec<T, rows>& operator[](u32 column) const
             {
                 return data[column];
@@ -187,7 +179,7 @@ namespace blt
              * Takes a value stored across a row, taking one from each column in the specified row
              * @param row the row to extract from. defaults to the first row
              */
-            [[nodiscard]] constexpr inline vec<T, columns> vec_from_column_row(blt::u32 row = 0) const
+            constexpr inline vec<T, columns> vec_from_column_row(blt::u32 row = 0) const
             {
                 vec<T, columns> ret;
                 for (blt::u32 j = 0; j < columns; j++)
@@ -195,6 +187,21 @@ namespace blt
                 return ret;
             }
             
+            /**
+             * Assign to this matrix from the row information in each column of a matrix
+             * Where columns can be assigned directly from each-other, row stored data must be assigned this way
+             * this was hacked together for an assignment and a better way is a TODO;
+             * @param to_column column in this matrix to assign to
+             * @param row the row place that the value is store in to assign from. Defaults to the first element in each column
+             */
+            template<blt::u32 p>
+            constexpr inline matrix_t& assign_to_column_from_column_rows(generalized_matrix<T, p, rows> mat, blt::u32 to_column, blt::u32 row = 0)
+            {
+                for (blt::u32 j = 0; j < rows; j++)
+                    data[to_column][j] = mat[j][row];
+                return *this;
+            }
+            
             constexpr inline matrix_t& operator+=(const matrix_t& other)
             {
                 for (blt::u32 i = 0; i < columns; i++)
@@ -357,16 +364,6 @@ namespace blt
                 return !(left == right);
             }
         
-            auto begin() const
-            {
-                return data.begin();
-            }
-            
-            auto end() const
-            {
-                return data.end();
-            }
-        
         private:
             blt::vec<T, rows> data[columns];
     };

include/blt/math/vectors.h

@@ -124,14 +124,6 @@ namespace blt
                 return elements[3];
             }
             
-            [[nodiscard]] constexpr inline vec<T, size> abs() const
-            {
-                auto copy = *this;
-                for (auto& v : copy.elements)
-                    v = std::abs(v);
-                return copy;
-            }
-            
             [[nodiscard]] constexpr inline T magnitude() const
             {
                 T total = 0;

include/blt/meta/iterator.h

@@ -122,8 +122,7 @@ namespace blt::meta
     
     template<typename Iter>
     struct is_reverse_iterator<std::reverse_iterator<Iter>> : std::true_type
-    {
+    {};
-    };
     
     template<typename Iter>
     inline constexpr bool is_reverse_iterator_v = is_reverse_iterator<Iter>::value;

include/blt/std/ranges.h

@@ -19,6 +19,151 @@
 
 namespace blt
 {
+    namespace itr
+    {
+        template<typename Begin, typename End>
+        class itr_container
+        {
+            public:
+                itr_container(Begin&& begin, End&& end): begin_(std::forward<Begin>(begin)), end_(std::forward<End>(end))
+                {}
+                
+                Begin begin()
+                {
+                    return begin_;
+                }
+                
+                End end()
+                {
+                    return end_;
+                }
+            
+            private:
+                Begin begin_;
+                End end_;
+        };
+        
+        // TODO: cleanup! all of this! add support for reversing
+        template<typename C1_TYPE, typename C2_TYPE>
+        class pair_iterator
+        {
+            public:
+                using c1_ref = blt::meta::deref_return_t<C1_TYPE>;
+                using c2_ref = blt::meta::deref_return_t<C2_TYPE>;
+                
+                using iterator_category = std::forward_iterator_tag;
+                using value_type = std::pair<c1_ref, c2_ref>;
+                using difference_type = blt::ptrdiff_t;
+                using pointer = void*;
+                using reference = value_type&;
+                using const_reference = const value_type&;
+                
+                explicit pair_iterator(C1_TYPE c1, C2_TYPE c2): current_c1_iter(c1), current_c2_iter(c2)
+                {}
+                
+                pair_iterator& operator++()
+                {
+                    ++current_c1_iter;
+                    ++current_c2_iter;
+                    return *this;
+                }
+                
+                bool operator==(pair_iterator other) const
+                {
+                    return current_c1_iter == other.current_c1_iter && current_c2_iter == other.current_c2_iter;
+                }
+                
+                bool operator!=(pair_iterator other) const
+                {
+                    return current_c1_iter != other.current_c1_iter || current_c2_iter != other.current_c2_iter;
+                }
+                
+                value_type operator*() const
+                {
+                    return {*current_c1_iter, *current_c2_iter};
+                };
+                
+                value_type operator*()
+                {
+                    return {*current_c1_iter, *current_c2_iter};
+                };
+            
+            private:
+                C1_TYPE current_c1_iter;
+                C2_TYPE current_c2_iter;
+        };
+    }
+    
+    template<typename Begin, typename End>
+    static inline auto iterate(Begin&& begin, End&& end)
+    {
+        return itr::itr_container<Begin, End>{std::forward<Begin>(begin), std::forward<End>(end)};
+    }
+    
+    template<typename Begin, typename End>
+    static inline auto reverse_iterate(Begin&& begin, End&& end)
+    {
+        return itr::itr_container{std::reverse_iterator(std::forward<Begin>(end)), std::reverse_iterator(std::forward<End>(begin))};
+    }
+    
+    template<typename C1_ITER, typename C2_ITER, template<typename, typename> typename iterator = itr::pair_iterator>
+    class pair_enumerator
+    {
+        public:
+            explicit pair_enumerator(C1_ITER c1_begin, C1_ITER c1_end, C2_ITER c2_begin, C2_ITER c2_end):
+                    begin_(std::move(c1_begin), std::move(c2_begin)), end_(std::move(c1_end), std::move(c2_end))
+            {
+                auto size_c1 = c1_end - c1_begin;
+                auto size_c2 = c2_end - c2_begin;
+                if (size_c1 != size_c2)
+                    throw std::runtime_error("Iterator sizes don't match!");
+            }
+            
+            iterator<C1_ITER, C2_ITER> begin()
+            {
+                return begin_;
+            }
+            
+            iterator<C1_ITER, C2_ITER> end()
+            {
+                return end_;
+            }
+        
+        private:
+            iterator<C1_ITER, C2_ITER> begin_;
+            iterator<C1_ITER, C2_ITER> end_;
+    };
+    
+//    template<typename T, typename G>
+//    static inline auto in_pairs(const T& container1, const G& container2)
+//    {
+//        return pair_enumerator{container1.begin(), container1.end(), container2.begin(), container2.end()};
+//    }
+//
+//    template<typename T, typename G>
+//    static inline auto in_pairs(T& container1, G& container2)
+//    {
+//        return pair_enumerator{container1.begin(), container1.end(), container2.begin(), container2.end()};
+//    }
+//
+//    template<typename T, typename G, blt::size_t size>
+//    static inline auto in_pairs(const T(& container1)[size], const G(& container2)[size])
+//    {
+//        return pair_enumerator{&container1[0], &container1[size], &container2[0], &container2[size]};
+//    }
+//
+//    template<typename T, typename G, blt::size_t size>
+//    static inline auto in_pairs(T(& container1)[size], G(& container2)[size])
+//    {
+//        return pair_enumerator{&container1[0], &container1[size], &container2[0], &container2[size]};
+//    }
+//
+//    template<typename T, typename G>
+//    static inline auto in_pairs(T&& container1, G&& container2)
+//    {
+//        return pair_enumerator{container1.begin(), container1.end(), container2.begin(), container2.end()};
+//    }
+    
     template<typename T>
     struct range
     {
@@ -94,6 +239,41 @@ namespace blt
             }
     };
     
+    template<typename I>
+    class itr_offset
+    {
+        private:
+            I begin_;
+            I end_;
+        public:
+            template<typename T>
+            itr_offset(I begin, I end, T offset): begin_(begin), end_(end)
+            {
+                for (T t = 0; t < offset; t++)
+                    ++begin_;
+            }
+            
+            template<typename C, typename T>
+            itr_offset(C& container, T offset): begin_(container.begin()), end_(container.end())
+            {
+                for (T t = 0; t < offset; t++)
+                    ++begin_;
+            }
+            
+            auto begin()
+            {
+                return begin_;
+            }
+            
+            auto end()
+            {
+                return end_;
+            }
+    };
+    
+    template<typename C, typename T>
+    itr_offset(C, T) -> itr_offset<typename C::iterator>;
+    
     inline constexpr std::size_t dynamic_extent = std::numeric_limits<std::size_t>::max();
     
     template<typename T, std::size_t extent = dynamic_extent>

tests/iterator_tests.cpp

@@ -23,7 +23,6 @@
 #include <blt/iterator/zip.h>
 #include <blt/iterator/enumerate.h>
 #include <blt/iterator/iterator.h>
-#include <blt/std/ranges.h>
 #include <blt/format/boxing.h>
 #include <array>
 #include <forward_list>
@@ -123,10 +122,6 @@ void test_enumerate()
 void test_pairs()
 {
     blt::log_box_t box(std::cout, "Pairs Tests", 25);
-    for (auto [a1, a2] : blt::in_pairs(array_1, array_2))
-    {
-        BLT_TRACE_STREAM << a1 << " : " << a2 << "\n";
-    }
 }
 
 void test_zip()
@@ -163,41 +158,6 @@ void test_zip()
     }
 }
 
-void test_iterate()
-{
-    blt::log_box_t box(std::cout, "Iterate Tests", 25);
-    for (auto v : blt::iterate(array_1))
-    {
-        BLT_TRACE_STREAM << "Element: " << v << "\n";
-    }
-    BLT_TRACE("================================");
-    for (auto v : blt::iterate(array_1).skip(5))
-    {
-        BLT_TRACE_STREAM << "Element: " << v << "\n";
-    }
-    BLT_TRACE("================================");
-    for (auto v : blt::iterate(array_1).take(5))
-    {
-        BLT_TRACE_STREAM << "Element: " << v << "\n";
-    }
-    BLT_TRACE("================================");
-    for (auto v : blt::iterate(array_1).rev())
-    {
-        BLT_TRACE_STREAM << "Element: " << v << "\n";
-    }
-    BLT_TRACE("================================");
-    for (auto [a, b] : blt::iterate(array_1).zip(list_1))
-    {
-        BLT_TRACE_STREAM << "Zip: " << a << " " << b << "\n";
-    }
-    BLT_TRACE("================================");
-    for (auto [i, data] : blt::iterate(array_1).zip(list_1).skip(3).take(4).enumerate())
-    {
-        auto [a, b] = data;
-        BLT_TRACE_STREAM << "Zip (" << i << "): " << a << " " << b << "\n";
-    }
-}
-
 int main()
 {
     test_enumerate();
@@ -205,6 +165,4 @@ int main()
     test_pairs();
     std::cout << std::endl;
     test_zip();
-    std::cout << std::endl;
-    test_iterate();
 }