How do I define it without defining it?
Is it similar to the if define in C language??
If you can find it in the PHP manual, please.
Like what:
defined('THINK_PATH') or define('THINK_PATH', dirname(__FILE__).'/');
Reply content:
How do I define it without defining it?Is it similar to the if
In Java EE applications, the data source object DataSource objects is a way to access relational databases through the jdbc api. Each DataSource object has a series of attributes used to describe the data source in the real world. These attributes can be used to describe the address, database name, network protocol, and other information of the database server. In addition, the data source object can be used with JNDI. If you bind a data source to a registered JNDI service, you can access the jn
Define section:Macros can be used instead of constant values, and can be used instead of expressions, even code snippets. (Macros are powerful, but error-prone, so their pros and cons are quite controversial.) )The syntax for a macro is:Macro value #define Macro nameAs a recommendation and a common practice for a broad range of programmers, macro names often use all uppercase letters.
Advantages of usi
# Ifndef/# define/# endif usage in c/c ++ header files,
Presumably many people have read "# ifndef/# define/# endif used in the header file to prevent this header file from being repeatedly referenced ". But can you understand the meaning of "being repeatedly referenced? What will happen if the header file is repeatedly referenced? Is it necessary to add # ifndef/# defi
Copy Code code as follows:
#include /*typedef char * string;
int main (void){String a[] = {"I", "like", "to", "Fight,"},B[] = {"Pinch,", "and", "Bight."};printf (%s%s%s%s%s\n ", A[0], a[1], a[2], a[3], b[0], b[1], b[2]);return 0;}
Replace the row of the TypeDef with #define, and the #define example that has been given cannot pass, but a single character can be added to the program.
====
The Magic usage of C + + macro commands.
First look at the following three statements:
#define CONN (x,y) x# #y
#define TOCHAR (x) #@x
#define TOSTRING (x) #x
1. # # Connection operator
# #表示连接 (token pasting, or token concatenation,merge two tokens into one while expanding macros). x# #y表示什么. Represents x connection Y, for example:
int n = Conn (123,456);
1) #define是preprocessing Directives, which is performed when the preprocessing is compiledsimple substitution, no correctness check, whether the meaning is correct or not, only when compiling the source program has been expanded to find possible errors and error.
For example: #define PI 3.1415926 Program: Area=pi*r*r will be replaced with 3.1415926*r*r if you write the number 9 in the #
Value of Do{}while (0) When macro definition (#define) in C languageRecently found in the code of the new company everywhere used do{...} while (0), Google a bit, found that stack overflow early on a lot of discussion, summed up the discussion, coupled with their own understanding, do{...} while (0) the value is mainly reflected in:1. Increase the adaptability of the CodeThe following macro definition does not use do{...} while (0)#
In applications, define is often used to define common parameter information to increase program readability and reliability.
In PHP, the constant name is a simple identifier, which cannot be changed during the execution period and is case sensitive by default. Constants are always capitalized.
Note: The third parameter in define can be used to set whether the co
ArticleDirectory
Introduction
1. Using a function
1.1. methods defined internally
1.2. Methods added to the prototype
2. Using Object literals
3. Singleton using a function
Summary
3 ways to define a javascript classintroduction
Javascript is a very flexible object-oriented language when it comes to syntax. in this article you can find three ways of defining and instantiating an object. even if you have already picked y
Original article link Try to use const and inline instead of # define
It is also called: Try to use the compiler instead of preprocessing.
Cause:
(1) # Define aspect_ratio 1.653Pre-compileProgramAspect_ratioReplace 1.653When a compilation error occurs, only the 1.653But aspect_ratio cannot be tracked., Not easy to debug
(2) # Define max (A, B) (a)> (B )? (
Document directory
Link definition order
Define a local link Style
Define link StyleCSS provides specific tools for some special effects, which are called "pseudo classes ". The following describes the four pseudo classes that are often used to define link styles. They are:
: Link
: Visited
: Hover
: Active
Because we n
increases the difficulty of project management. IBM Rational Unified Process is implemented to manage and distribute the entire project development process. It is browser-based, A Customizable software development process platform. It focuses on the software development industry-recognized Optimization Method and manages the allocation of different elements in the development process. Generally, the default RUP can meet the needs of some users. Users can publish and use it simply by deleting
# DefineAndConstDifference
Although they feel "almost" in use, what are their differences in implementation?
See the following code:
# Define T 13/* use # A constant defined by define T */
Int main ()
{
Const int T = 13;/* a constant defined by const */
Int n = T;/* assign t to N */
Int M = T;/* assign t to M */
}
1.Difference:
The biggest difference between const and #
[Code sea shell TC] Use View to define dynamic Class, sea shell tcPreface
In TC,
Persistent Class corresponds to Table.
Define a Persistent Class. updatedb generates the corresponding table.
In the development environment of TC, a corresponding username will generate a table under this username
In the formal environment, because adm, su, and key are used, the corresponding table will be generated under thes
PHP uses array_fill to define multi-dimensional arrays. array_fill is multi-dimensional. PHP uses array_fill to define multi-dimensional arrays. array_fill this article describes how PHP uses array_fill to define multi-dimensional arrays. Share it with you for your reference. Specific Analysis: for example, PHP uses array_fill to
The Meaning of # # # in C++/C macro definition (define)# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # define.#是字符串化的意思, the # that appears in the macro definition is a string that is followed by a parameter;eg#define STRCPY__ (DST, SRC) strcpy (DST, #src)Strcpy__ (BUFF,ABC) equivalent to strcpy__ (buff, "abc")# #是连接符号, connect the paramet
First, #define宏定义1. Macro definition, like this is the macro definition: #define PI 3.14159;2. Macro Definition Format: Macro value #define Macro name is the macro to be defined, usually denoted by a meaningful name in uppercase, and the macro value is the constant represented by the macro. ;3. #define是预编译指令;4. The ess
After reading some frameworks, many of them use define to define many system parameters at the system core entrance. However, we recently see that some of them are defined in $ _ SERVER and even $ _ ENV. Although all functions can be implemented, I have been confused. What are the advantages of this definition? Or... after reading some frameworks, many of them use defin
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
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