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      std::counted_iterator<I>::operator++,+,+=,--,-,-=

      From cppreference.com
      <cpp‎ |iterator‎ |counted iterator
       
       
      Iterator library
      Iterator concepts
      Iterator primitives
      Algorithm concepts and utilities
      Indirect callable concepts
      Common algorithm requirements
      (C++20)
      (C++20)
      (C++20)
      Utilities
      (C++20)
      Iterator adaptors
      Range access
      (C++11)(C++14)
      (C++14)(C++14)  
      (C++11)(C++14)
      (C++14)(C++14)  
      (C++17)(C++20)
      (C++17)
      (C++17)
       
      std::counted_iterator
      Member functions
      counted_iterator::operator++counted_iterator::operator++(int)counted_iterator::operator+counted_iterator::operator+=counted_iterator::operator--counted_iterator::operator--(int)counted_iterator::operator-counted_iterator::operator-=
      Non-member functions
      (C++20)(C++20)
      (C++20)
      (C++20)
      (C++20)
      (C++20)
      Helper classes
       
      constexpr counted_iterator& operator++();
      		 (1)(since C++20)
      constexpr decltype(auto) operator++(int);
      		 (2)(since C++20)
      constexpr counted_iterator operator++(int)
          requiresstd::forward_iterator<I>;
      		 (3)(since C++20)
      constexpr counted_iterator& operator--()
          requiresstd::bidirectional_iterator<I>;
      		 (4)(since C++20)
      constexpr counted_iterator operator--(int)
          requiresstd::bidirectional_iterator<I>;
      		 (5)(since C++20)
      constexpr counted_iterator operator+(std::iter_difference_t<I> n)const
          requiresstd::random_access_iterator<I>;
      		 (6)(since C++20)
      constexpr counted_iterator& operator+=(std::iter_difference_t<I> n)
          requiresstd::random_access_iterator<I>;
      		 (7)(since C++20)
      constexpr counted_iterator operator-(std::iter_difference_t<I> n)const
          requiresstd::random_access_iterator<I>;
      		 (8)(since C++20)
      constexpr counted_iterator& operator-=(std::iter_difference_t<I> n)
          requiresstd::random_access_iterator<I>;
      		 (9)(since C++20)

      Increments or decrements the underlying iteratorcurrent and the distance to the endlength.

      The behavior of these functions is undefined if thelength would be set to a minus value.

      1) Pre-increments by one. Equivalent to++current;--length;return*this;.
      2) Post-increments by one. Equivalent to--length;try{return current++;}catch(...){++length;throw;}.
      3) Post-increments by one. Equivalent tocounted_iterator temp{*this};++*this;return temp;.
      4) Pre-decrements by one. Equivalent to--current;++length;return*this;.
      5) Post-decrements by one. Equivalent tocounted_iterator temp{*this};--*this;return temp;.
      6) Returns an iterator adaptor which is advanced byn. Equivalent toreturn counted_iterator(current+ n, length- n);.
      7) Advances the iterator adaptor byn. Equivalent tocurrent+= n; length-= n;return*this;.
      8) Returns an iterator adaptor which is advanced by-n. Equivalent toreturn counted_iterator(current- n, length+ n);.
      9) Advances the iterator adaptor by-n. Equivalent tocurrent-= n; length+= n;return*this;.

      Contents

      [edit]Parameters

      n - the number of positions to increment or decrement the iterator adaptor

      [edit]Return value

      1)*this
      2,3) A copy of*this that was made before the change.
      4)*this
      5) A copy of*this that was made before the change.
      6) An iterator adaptor which is advanced byn.
      7)*this
      8) An iterator adaptor which is advanced by-n.
      9)*this

      [edit]Example

      Run this code
      #include <cassert>#include <initializer_list>#include <iterator> int main(){constauto v={1,2,3,4,5,6};std::counted_iterator<std::initializer_list<int>::iterator> it1{v.begin(),5}; ++it1;assert(*it1==2&& it1.count()==4);// (1)auto it2= it1++;assert(*it2==2&&*it1==3);// (3)--it1;assert(*it1==2&& it1.count()==4);// (4)auto it3= it1--;assert(*it3==2&&*it1==1);// (5)auto it4= it1+3;assert(*it4==4&& it4.count()==2);// (6)auto it5= it4-3;assert(*it5==1&& it5.count()==5);// (8)    it1+=3;assert(*it1==4&& it1.count()==2);// (7)    it1-=3;assert(*it1==1&& it1.count()==5);// (9)}

      [edit]See also

      (C++20)
      		 advances the iterator
      (function template)[edit]
      (C++20)
      		 computes the distance between two iterator adaptors
      (function template)[edit]
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