Fundamentally understand typedef

1. typedef int size_t;
Most books and teachers will talk about this statement. This is the alias for defining size_t as an int. That is, typedef a B. B is the alias of.
The result is correct, but it is not necessarily correct in terms of grammar. It cannot be understood as follows:

2. typedef int int_array [4];
Int_array A, B;
If you understand this, see:

3. typedef int (* PF) (const char *, const char *);
PF register (PF );
If you understand this, the following content is not prepared for you. If you do not understand, please refer to: (here I will try to explain it as much as possible)

If you think the following statement is troublesome:
Int A [4], B [4], C [4];
You want to simplify or hide complex types through the following statement:
Int_array A, B, C;
The method to use typdef is as follows:
1. Find the generic format you want to declare. For example, int A [4], B [4], C [4]; only A, B, and C are different, they have the same declarative mode int <Name> [4];
2. Use the new type name you want to declare to replace the change section in the general format. For example, the position of A, B, and C is replaced by the new type int_array, And the typedef symbol is added to the front, that is:
Typedef int int_array [4];
3. When you want to declare the, B, and C Types in the int_array position above, you can use the following statement:
Int_array A, B, C;

Simply put, in a defined typedef <string>;, an undefined type name type_a appears in the <string>. When you use this typedef:
The meaning of type_a object is that you actually declare to replace type_a in <string> with the object name.
For example, typedef int int_array [4];
Int_array object;
In fact, the statement you wrote is: Replace the string "int int_array [4];" with the int_array in the object to get the result: int object [4];
This is how the compiler processes the tyepdef definition.

After this explanation, you should easily understand the function pointer typedef. Is it very simple!

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