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      std::span<T,Extent>::front

      From cppreference.com
      <cpp‎ |container‎ |span
       
       
       
       
      constexpr reference front()const;
      		(since C++20)

      Returns a reference to the first element in the span.

      Ifempty() istrue, the behavior is undefined.

      		(until C++26)

      Ifempty() istrue:

      • If the implementation ishardened, acontract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined.
      • If the implementation is not hardened, the behavior is undefined.
      		(since C++26)

      Contents

      [edit]Return value

      A reference to the first element.

      [edit]Complexity

      Constant.

      [edit]Notes

      For a spanc, the expressionc.front() is equivalent to*c.begin().

      [edit]Example

      Run this code
      #include <iostream>#include <span> void print(std::span<constint>const data){for(auto offset{0U}; offset!= data.size();++offset)std::cout<< data.subspan(offset).front()<<' ';std::cout<<'\n';} int main(){constexprint data[]{0,1,2,3,4,5,6};    print({data,4});}

      Output:

      0 1 2 3

      [edit]See also

      access the last element
      (public member function)[edit]
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