STL Program Design Practice 4: Simplify input and improve maintainability

STL Program Design Practice 4: Simplify input and improve maintainability

STL is stored in the STD space of the C standard library. When you use the type in the STD space, you must add std ::, otherwise you must add the following statement in the program:

Using namespace std;

Introduce STD to the global space, so you don't have to enter std ::, it is convenient for us to enter. But when you need to use a container in STL, when you are named a certain type of object, such as:

Vector Vectstr;

Named a constant iterative:

Vector :: const_iterator cvectstr_it;

You have to enter a bunch of long characters, especially if the number of times is frequent. In order to reduce the input you should be named an alternate type. Such as:

TypedEf Vector Vect_Str;

Typedef Vector :: const_iterator cvect_str_it;

This way you can greatly reduce the input when you have a good name object, but also make the code clear.

Vect_str vstrobj;

CVECT_STR_IT CVSTR_IT;

Significant alternative types can not only reduce repeated input, concise code. The most important thing is to improve the maintenanceability of the code, just as the following package size macro is defined in TCP / IP programming:

#define packsize sizeof (struct _tagspecpack);

When you define such a macro, no matter where you need to use a package size parameter, you will be incomugged in the Packsize Macro. The benefits of this should all know that no matter how your message structure is modified, increased or decrease, your program can be compiled without any modifications, because the packsize macro always can pass the correct packet size information. . Use the TypeDef to repay the alternative type with the same integrity. Do not believe let us take a look.

Good programmers will maximize the library, high-density use libraries, bring us great convenience, avoiding duplication of labor, saving time. Especially the emergence of STL, many programmers will write the following code:

Class Custom

{

Vector m_vset;

Vector :: item m_it;

PUBLIC:

Vector getData () {return m_vset;}

......

}

This implementation does not have a big problem (please don't say that the getData function should be written, or there is no need, just example, just explaining that it is very likely to appear in the Custom class. Vector , even more. ), But its maintenance is relatively poor. If for some reason, the Custom class wants to replace the container type (possibly to use some algorithm, such as Lower_Bound). At this time, you have to check the entire class and member function, one one replaces the dead Vector (damn Ctrl C, Ctrl V). It's not worth it if it is stupid for this.

Let us see the extensive extensive extensive application of Typedef applications in STL, I believe that so much more convincing.

Template

Class allocator {

TYPEDEF SIZE_T SIZE_TYPE;

TYPEDEF PTRDIFF_T DIFCERENCE_TYPE;

Typedef t * pointer;

Typedef const t * const_pointer;

TYPEDEF T & REFERENCE;

Typedef const_t_reference; typedef t value_type;

......

Ok, let's talk about it, I hope to help everyone. This article is for reference only. The rush of the article, there is a typison or error, please tell us to point out ccplusplus@21cn.com, thank you first. Welcome to communicate with you and make progress together. (- Yuan Xiakai -)

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If the friends have more STL knowledge, I hope to advise, I am grateful.