std::span<T,Extent>::front
| constexpr reference front() const; | 
Returns a reference to the first element in the span.
Calling front on an empty span results in undefined behavior.
Parameters
(none).
Return value
A reference to the first element.
Complexity
Constant.
Notes
For a span c, the expression c.front() is equivalent to *c.begin().
Example
See also
| access the last element (public member function) | 
    © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
    http://en.cppreference.com/w/cpp/container/span/front