std::span<T,Extent>::front - cppreference.com (original) (raw)
| constexpr reference front() const; | | (since C++20) | | ---------------------------------- | | ------------- |
Returns a reference to the first element in the span.
| If empty() is true, the behavior is undefined. | (until C++26) |
|---|---|
| If empty() is true: If the implementation is hardened, a contract 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) |
[edit] Return value
A reference to the first element.
[edit] Complexity
Constant.
[edit] Notes
For a span c, the expression c.front() is equivalent to *c.begin().
[edit] Example
#include #include void print(std::span const data) { for (auto offset{0U}; offset != data.size(); ++offset) std::cout << data.subspan(offset).front() << ' '; std::cout << '\n'; } int main() { constexpr int data[]{0, 1, 2, 3, 4, 5, 6}; print({data, 4}); }
Output:
[edit] See also
| | access the last element (public member function) [edit] | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |