For example, the program file starts with the following # define statement.
Copy codeThe Code is as follows: # define N 10
# Define PI 3.14
# Deprecision MAX 10000
# Define Heigth 6.65
...
...
If the program runs an error here, and there is an error when we use these constants, the editor should throw an error message
This article mainly introduces how to use hidef extension in PHP to replace define to improve the performance. This article focuses on testing the performance of hidef and introduces the installation method and examples, if you need a new constant, you can refer to the website to open the local config. php file, think of hidef tested a few years ago and apc to improve define performance.
In my program, the
This article provides a detailed analysis of the differences between static, const, and define in php. For more information, see
Define section:Macros can be used not only to replace constant values, but also to replace expressions or even code segments. (Macros have powerful functions but are prone to errors, so their advantages and disadvantages are quite controversial .)
Macro syntax:#
In C/C ++, we usually write
Program The typedef keyword and # define macro definition commands may often be used. In some cases, using them will achieve the same effect, but they have substantial differences, A keyword is C/C ++, a macro definition command is C/C ++, and typedef is used to create an alias for an existing data type, # define is used to define a m
In C/C ++, we usually use typedef keywords and # define macro-defined commands to write programs. In some cases, using them will achieve the same effect, however, there are substantial differences. One is the keywords of C/C ++ and the other is the macro definition commands of C/C ++, typedef is used to create an alias for an existing data type, and # define is used to
at the time of definition ;(2) After initialization of the constant variable, it is not allowed to be assigned again ;4. Example#include Operation Result: $Third, const (c + +) and # define language 1. The constants defined by the const are different from the symbolic constants defined by # define(1) constants defined by a const have a type, whereas a # define d
Const
Used to define constant values that cannot be changed at run time. Once defined and cannot change its value, an error occurs if the value is changed in the program.
The code is as follows
Copy Code
CALSS math{Const pi=3.14159;}echo Math::p i;?>
There is no dollar sign ($) before and can be useful without initializing the class. The constant value must be a constant expression. const-defined variables that
#define EC (x) l# #x role Description
Indicates L is connected with X.
#define CONN (x,y) x# #y
#define TOCHAR (x) #@x
#define TOSTRING (x) #x
x# #y表示什么? Represents x connection Y, for example:
int n = Conn (123,456); The result is n=123456;
char* str = Conn ("asdf", "ADF") the result is str = "ASDFADF";
It's a
Macro definition in C # define usage,
# Define is a macro definition Command provided in C language. Its main purpose is to provide programmers with some convenience in programming and improve the program running efficiency to a certain extent, however, when learning this command, students often cannot understand the essence of the command, and there is always some confusion here. The command is misused dur
# Define is a macro definition Command provided in C language. Its main purpose is to provide programmers with some convenience in programming and improve the program running efficiency to a certain extent, however, when learning this command, students often cannot understand the essence of the command, and there is always some confusion here. The command is misused during programming, so that the program runs differently from the expected purpose, or
When defining constants in PHP, you can use both the const and define methods, so what's the difference between them?1.const the definition of a class member variable, once defined, cannot be modified. Define is not available for definition of class member variables and can be used for global constants.2.const can be used in a class, define cannot.3.const You can
Define section:Macros can be used not only to replace constant values, but also to replace expressions or even code segments. (Macros have powerful functions but are prone to errors, so their advantages and disadvantages are quite controversial .)
Macro Syntax:# Define macro name macro value
As a suggestion and a common habit of programmers, macro names often use uppercase letters.
Advantages of macros:1)
Difference between const and # define,
(1) Different compiler Processing MethodsThe define macro is expanded in the preprocessing phase.
Const constants are used in the compilation and running phase.
(2) Different Types and security checks
The define macro has no type and does not check any type. It just expands.
Const constants have specific types. during compil
This article mainly introduces how to use mini-define to implement modular management of front-end code. it is a very good article. we recommend it to partners who need it.
Mini-define
A simple front-end modular framework based on require. If you don't want to spend time learning require. js or look at the long cmd/amd specifications, then this mini-define is yo
Correct use of IOS macros (define) and constants (const)In iOS development, macro definitions are often used, or some data types are modified 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 distinguish between the following? Do you know when to use it?#define Hscoder @"Hansha haha"nsstring *hscoder = @
Define section:Macros can be used not only to replace constant values, but also to replace expressions or even code segments. (Macros have powerful functions but are prone to errors, so their advantages and disadvantages are quite controversial .)Macro Syntax:# Define macro name macro valueAs a suggestion and a common habit of programmers, macro names often use uppercase letters.Advantages of macros:1) make
Not only can you define constants in C + + define , but you can also const define constants with the following differences:
A #define MAX 255 defined constant is no type, given an immediate number, the compiler simply links the defined constant value to the name of the defined constant,
Requirejs file Download, select the version you need toRequirejs using instance Step1 to define an HTML fileWe need to define an HTML file named requirehtml.html.Under File content"">"Utf-8"> "Viewport"Content="Width=device-width, initial-scale=1.0"> introduction of require file,../refers to the parent directory of the directory where the current requirehtml.html file resides. Here is the require.js file un
First, the key:1,Inline functions are the same in readability as functions, while at compile time the functions are embedded directly into the body of the caller, eliminating the call/return instruction, which is faster at run time.
2,Inline functions can be debugged, and macro definitions cannot be debugged.
Inline functions and macros are essentially two different concepts if a program writer has a requirement for both fast and readable conditions, the function should be crowned inline. The
Define section:Macros can be used not only in place of constant values, but also in substitution of expressions or even code snippets. (Macros are powerful, but they are also prone to errors, so the pros and cons are quite controversial.) )
The syntax for macros is:#define Macro Name Macro value
As a suggestion and a common habit of programmers, macro names often use all uppercase letters.
Advantages of
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