# Extra Clang Tools 4 documentation

## clang-tidy - readability-container-size-empty

# readability-container-size-empty

Checks whether a call to the `size()` method can be replaced with a call to `empty()`.

The emptiness of a container should be checked using the `empty()` method instead of the `size()` method. It is not guaranteed that `size()` is a constant-time function, and it is generally more efficient and also shows clearer intent to use `empty()`. Furthermore some containers may implement the `empty()` method but not implement the `size()` method. Using `empty()` whenever possible makes it easier to switch to another container in the future.

The check issues warning if a container has `size()` and `empty()` methods matching following signatures:

code-block:: c++

> size_type size() const; bool empty() const;

size_type can be any kind of integer type.