Auto

Although C++ is a typed language, you can use auto when initializing a variable to determine the type automatically. This feature was introduced in C++14 and does not work with older versions.
Here is an example:

Note that it is harder to catch errors when using auto. Consider the example:

Specifying types would help us understand code better and find what's wrong:

Note

Any of num1, num2 or num3 should be float to output the correct result.

Nevertheless, auto is widely used in range-based for loops since it is a versatile method of iterating over arrays and other containers. Just use the following syntax for iterating over arr:

It also can be used when the type is long to type but is clear from the context and can't lead to incorrect results.