How to use static_cast to convert a left value to a right value

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Use std::move

Examine the following two functions:

It is the same except that one of the parameter types is a left value reference and the other is a right value reference. Combined with the previous article, we can draw the following conclusion: the left value reference indicates that the value may be modified, and the right value reference is the right to take over the parameter data. Accordingly, in the case of a reference to the right value, the caller is required to explicitly waive the right.

The way to waive your rights here is through the std::move function, as you did in the fr function in the figure above.

Understand std::move

Here is the source code for std::move:

Looking at the function body first, you only do one thing: use static_cast to explicitly convert argument t to another type, which is:

Typename is used to indicate that the following expression is a type rather than a variable, ignore it first, then remove the negative & & (forget about it for the time being), and the code looks like this:

We know (and will let you know if we don't know) that the function of remove_reference is to remove reference type modifiers.

For example: return int; if the type of T is int& or int&&, and return int if the type of T is int

Considering the & & modifier you just ignored, you can conclude that the target type of static_cast is the input type T, which removes possible reference modifiers, and then adds right-value reference modifiers.

In other words, the function of std::move is to use static_cast to explicitly convert T.m.m.T.T.m.m.cn.

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