define sinkhole

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

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 cann

When data is inserted, Oracle considers it as a variable and requires a value. The reason is that Oracle defines as a custom variable.SQL> show all Appinfo is off and set to "SQL * Plus" Arraysize 15 Autocommit off Autoprint off Autorecovery off Autotrace off Blockterminator "." (hex 2e) Btitle off and is the first few characters of the next SELECT statement Eclipsep off Colsep "" Compatibility version native Concat "." (hex 2e) Copycommit 0 Copytypecheck is on

Read the manual that define defines constants that allow only: Only scalar and null are allowed. The type of scalar is integer, Float,string, or Boolean. It is also possible to define a constant value of type resource, but it is not recommended to do so, which can lead to the occurrence of an unknown condition. Read the PHP source code today, found that the second parameter of

I often encounter defining global constants when I brush a question. I usually use # define (probably because of the very little contact with the const reason)As usual, when we did 51nod1082 yesterday, the violence was defined most by # define. But the submission timed out .....Later to see others write when the definition of the global use is a const so Baidu the difference between the two(1) different com

Code test Environment: Hadoop2.4Application scenario: This technique can be used when custom output data formats are required, including the presentation of custom output data. The output path. The output file name is called and so on.The output file formats built into Hadoop are:1) fileoutputformat2) textoutputformat3) sequencefileoutputformat4) multipleoutputs5) nulloutputformat6) lazyoutputformatSteps:Similar input data format, you can define the s

I only want to solve the speed problem. I don't mention the usage for the moment. someone on the Internet said that Const is a structure syntax and the speed will be several times higher than the define function. I need a professional saying, is that true? Currently, const can be used outside the class. Will it be used preferentially when you define constants? I only want to solve the speed problem. I don't

The difference between define and defined in PHP the difference between define and defined in PHP will confuse the two functions for beginners? 1. define is used to define a constant. constants are also within the global range. You can access constants anywhere in the script without specifying the scope. Once a constan

: This article mainly introduces the difference between const and define (PHP). If you are interested in the PHP Tutorial, please refer to it. Description: const is used to define the class member variables. at the same time, const itself is a language structure, and define is a function. const is much faster than define