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What this means is actually equivalent to the fact that you can replace the preprocessor with a compiler.Because using a preprocessor may make it impossible for the processed things to enter the symbol table, for example #define MaxLen 16 Here The MaxLen does not enter the symbol table, so there is a compile error when the prompt is 16 instead of MaxLen, which brings a lot of errors. For the above formula, you can try to use a constant to replace the

In iOS development, it is often used to define macros, or to modify some data types with const, and often developers do not know how to use them correctly, resulting in the confusion of macros and const decorations in the project.Can you tell the difference between the following? Do you know when to use it?#define Hscoder @ "Hansha haha"NSString*hscoder = @"Hansha haha";extern NSString*hscoder;extern Const

typedefIf it is placed outside all functions, its scope is from the beginning of its definition until the end of the file;If placed within a function, the defined field is defined from the beginning of the definition until the end of the function;#define:Scopes are defined from the beginning of the definition to the end of the entire file, whether within a function or outside of all functions.Define within the same compilation unit, even in different namespaces, the scope of the action is the sa

The difference is as follows: Constants defined with #define MAX 255 are of no type , given an immediate number, and the compiler simply links the defined constant value to the name of the defined constant, define the defined macro variable to be replaced at the time of preprocessing. Copy replacement is used where the constant is applied in the program; with const float MAX = 255; The defined constants hav

of an interesting thing to do, but the way we often use to create objects in object-oriented objects is: Car car=new car (); Using the New keyword is already popular, so we use the above method to define total feeling awkward, and to create new attributes and functions every time we call them, it is not practical. Down we look at the form definition class of the constructor. 2. Constructors This approach looks a bit like a factory function. The s

1. Define a simple constant: Define a constant to facilitate modification. (do not add a semicolon to the end !) # Define n 1000 is equivalent to const int n = 1000, but slightly different, define is just a simple replacement, rather than using it as a quantity. 2. defining simple functions: note that brackets are ofte

We should be familiar with the span tag, but it is very troublesome to use it, especially when we need to define the width and height for it, html pages often use the span tag, however, some friends may not use this label well. They seem to find it useful, but it is very troublesome to use it, especially when you need to define its width and height. A friend once asked:Why does the width and height of sp

To write a good C language, a beautiful macro definition is very important. Macro definitions can help us prevent errors, improve code portability and readability, and more.In the software development process, there are often common or common functions or code snippets that can be written as functions or encapsulated as macro definitions. So is the function good or the macro definition good? This requires us to make a reasonable choice between the two.Let's look at an example, compare two number

Avascript learn several ways to define objects in JSTransferred from: http://www.cnblogs.com/mengdd/p/3697255.htmlThere is no concept of class in JavaScript, only objects.　　There are several ways to define an object in javascript:1. Extending its properties and methods based on existing objects2. Factory mode3. How to construct a function4. Prototype ("prototype") mode5. Dynamic Prototyping ModeI. Extending

[Conversion] understanding # define sreg (* (volatile unsigned char *) 0x5f)This definition is always very strange. I don't know why. I have a little bit of experience today. Please submit more bricks to the prawns ~~~ Embedded system programming requires programmers to use C language to access a fixed memory address. Since it is an address, according to the syntax rules of the C language, the number of addresses should be pointer type. Therefore, aft