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What are the advantages of using an array to define constants? in this post, we finally edited tp_2015_1 from 2015-05-2221:29:28 to see how to define constants using arrays in the graph. I always feel so much trouble, why don't I write a constant directly, such as define (ATTACH_MALBUM, shopmember)? How good is it, but it's hard to get the whole array. what is th

You can use macros to define "functions" without return values ". For example: # Define printmax (A, B)/do/{/INT x = A, y = B;/printf ("MAX: % d/N", x> Y? X: Y); //} while (0) //... printmax (3, 4 ); Such a "function" is essentially different from a function in the true sense, because a macro is a pre-compilation behavior and only replaces the text before compilation. In Python source code, we often see

define the best Cache-control policy Follow the decision tree above to determine the best cache policy for the specific resource or set of resources your app uses. Ideally, your goal should be to cache as many responses as possible on the client, cache as long as possible, and provide a validation token for each response to enable efficient re-validation. Cache-control Instructions and instructions max-age=

1. Custom Constants * Must be defined with function define ()* The value can not be changed after the definition is finished* Use the constant name directly, not as a variable in front plus $sFor example: Define ("PI", 3.14); Define a constant$area = Pi*r*r; Calculate the area of a circleDefine ("URL", "http://www.jb51.net");echo "My URL is:". URL; 2 System con

#define是C的指令, used to define aliases for various data types, similar to TypeDef, but with a few different1,typedef is limited to defining a symbol name for a type, and # define can define not only the symbol name for the type, but also the alias for the value, such as 1 to true;The 2,typedef is interpreted by the compi

If you want to learn ExtJS well, it is necessary for JavaScript, that is, understanding the ExtJS underlying infrastructure. So now we're going to start learning the EXTJS infrastructure. How to create an ext class, create a complex flow of classes -Deep analysis of ext.js and Ext-more.js -Ext extensions to native JavaScript classes -EXT Operations DOM -Ext starts responding to events ways to define classes: DefineFor the ext4.x version, the

Recently a product debugging found a problem, together to check a small partner's C program. The problem is not big, but it exposes a little problem. For example: portb=0x23; He means to place the 5th and 2nd digits 1, but can you see the 5th and 2nd position 1? In fact, it should be 0x24, he did not find this error, calculated wrong, so the correct is: portb=0x23; In fact, we can completely avoid this mistake. Open our compiler's own header file, such as the AVR TINY13 header file has the follo

A constant is an identifier (first name) of a simple value. As the name implies, the value cannot be changed during script execution (except for the so-called magic constants, they are not constants). Changshime is considered to be case sensitive. Usually, constant identifiers are always uppercase. You can use the Define () function to define constants. After PHP 5.3.0, you can use the Const keyword to

#ifndef#define#endif的用法#ifndef#define#endif的用法  你所遇到的这几个宏是为了进行条件编译。一般情况下，源程序中所有的行都参加编译。但是有时希望对其中一部分内容只在满足一定条件才进行编译，也就是对一部分内容指定编译的条件，这就是“条件编译”。有时，希望当满足某条件时对一组语句进行编译，而当条件不满足时则编译另一组语句。     条件编译命令最常见的形式为：     #ifdef 标识符     程序段1     #else     程序段2     #endif         它的作用是：当标识符已经被定义过(一般是用#define命令定义)，则对程序段1进行编译，否则编译程序段2。     其中#else部分也可以没有，即：     #ifdef     程序段1     #

Difference between typedef and define The following code is used to describe Typedef char * typedef_char;# Define define_char char * // No semicolon here Void main (INT argc, char * argv []){Char s [] = "ASDF ";Const typedef_char P = s; // char * const* P = 'B'; // The P pointer is a constant pointer. It cannot point to anything else, but the content to which it points can be changed. Cout Const define_c

1) #define是预处理指令, in the compilation preprocessing simple substitution, does not make the correctness check, does not have the meaning whether correctly still to carry in, only has in the compilation has been expanded the source program only then discovers the possible error and errors. Like what:#define PI 3.1415926In the program: Area=pi*r*r will be replaced with 3.1415926*r*rSuppose you write the number

1) #define是预处理指令, in the compilation preprocessing simple substitution, does not make the correctness check, does not have the meaning whether correctly still brings in, only when compiles the already expanded source program only then discovers the possible error and error. For example:#define PI 3.1415926In the program: Area=pi*r*r will be replaced with 3.1415926*r*rIf you write the number 9 in the #

Define is a pre-processing command in C language. It is used for macro definition, which can improve the readability of the source code and provide convenience for programming. Pre-processing commands start with "#", for example, include commands # include and macro-defined commands # define. Usually put in front of the source file, which is called preprocessing. Preprocessing refers to the work done before

1 :__ file __,__ line __, macro expanded, Middle Layer Macro _ File _ is the predefine macro of the compiler, indicating the absolute path of the file, but ASCII characters. Suppose you want to convert _ file _ into a wide character. Maybe you want # DEFINE _ wfile _ L ##__ file __ Wchar_t pszfilepath [] =__ wfile __; In this case, the compiler will prompt that "l1_file _" is an undeclared identifier. Why? If the parameter after # Is a macro, # will

Brief introductionThis article is intended to describe how to define a Python source file encoding. The Python interpreter can parse the current file based on the encoding information specified. Typically, this approach improves the parser's recognition of Unicode-encoded source files and supports writing Unicode encodings, such as using UTF-8 in an editor that supports Unicode encoding.ProblemIn python2.1, Unicode encoding can only be achieved by mea

Define variables in the C header file and variables in the C Language I recently looked at a PHP extension source code and encountered a problem during compilation: ld: 1 duplicate symbol for architecture x86_64 After carefully reading the source code, we found that the definition of global variables appeared in the header file. ZEND_DECLARE_MODULE_GLOBALS(xx) Easy to understand // t1.h#ifndef T1_H#define T

#define aspect_ratio=1.1Const Double aspectratio=1.11. Using a macro causes the preprocessor to unconditionally replace the Aspect_ratio in the program code with 1.1, the compiler has never seen Aspect_ratio, debug compilation can be difficult to track, and the const constant resolves the problem.2. The scope of the macro definition is the subsequent compilation process until it is #undef, so the macro definition cannot be used as an exclusive constan

(1) What is an inline function?An inline function is a member function that is defined within a class, that is, the function body of the function is placed inside the class.(2) Why inline functions are introduced?Of course, the main purpose of introducing inline functions is to solve the efficiency problem of function calls in the program.In addition, we talked about the macro in the front, there is such an example:#define ABS (x) ((x) >0? (x):-(x))Wh