define tachyon

(1) different compiler processing methodsDefine macros are expanded during the preprocessing phase.Const constants are used during the compile run phase.(2) Different types and security checksDefine macros have no type, do not do any type checking, just expand.Const constants have specific types that perform type checking during the compilation phase.(3) different storage methodsThe Define macro is only expanded, how many places are used, how many tim

Static I. backgroundCause: when the program executes the variable defined in the function to its definition, the compiler allocates space for it on the stack, the space allocated by the function on the stack is released at the end of the function execution. This creates a problem: If you want to save the value of this variable in the function to the next call, how to implement it?The easiest way to think of is to define a global variable, but defining

I. Usage of typedef: ①Define a type of Alias, not just a simple macro replacement. It can be used to declare multiple objects of the pointer type at the same time. Trap: typedef char * tchar; Tchar Pa, PB; // Pa and Pb are pointer types. # Define cannot achieve this effect. Trap: typedef char * pstr; Int mystrcmp (const pstr, const pstr); const pstr is equivalent to char? No, it is actually equivalent to ch

In PHP constant and define are constants then I would like to introduce a method to achieve dynamic use of constant and define value method, I hope you have some help. How do you use PHP to show or use dynamic Constant/define values? Ex: The following example is a dynamic variable, but how is dynamic Constant used? The code is as follows Copy Code

PHP defines several constants in advance and provides a mechanism to define them at run time. Constants and variables are basically the same, and the difference is that constants must be defined with the Define function, which, once defined, cannot be redefined. Pre-defined constants in PHP: __file__ The file name of the script currently being processed. If used in a contained file, then its value is the co

A static 1) Background Cause: when the program executes the variable defined in the function to its definition, the compiler allocates space for it on the stack, the space allocated by the function on the stack is released at the end of the function execution. This creates a problem: If you want to save the value of this variable in the function to the next call, how to implement it? The easiest way to think of is to define a global variable, but defi

# Define e_pointer _ hresult_typedef _ (0x80004003l) # Define e_invalidarg _ hresult_typedef _ (0x80000003l) # Define e_notimpl _ hresult_typedef _ (0x80004001l) 2147746321 # Define co_e_failedtogetwindir _ hresult_typedef _ (0x80040211l)# Define vfw_e_sizenotset (hresult) 0

First, #define1. Just as an identifier:#define作为标识符时是没有参数的2, as a macro:the difference between #define as a macro and it as an identifier is that the macro has parameters and the identifier does notFor example: #define MAX (x, y) > (Y)? ( X):(Y))The difference between a macro and a function1, macro in use (compile phase) will be directly replaced (that is, simple

PHP uses array_fill to define multi-dimensional arrays. PHP uses array_fill to define multi-dimensional arrays. This article mainly introduces how PHP uses array_fill to define multi-dimensional arrays. The example shows how to use the array_fill function in php, has a PHP method to define multi-dimensional arrays usin

1. define the constant define (quot; constantquot;, quot; helloworld. quot;); constants can only contain scalar data (boolean, integer, floa... 1. define the constant define ("constant", "hello world. "); Constants can only contain scalar data (boolean, integer, float, and string ). When calling a constant, you only n

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