Name lookup of C ++: qualified name lookup1. Introduction
In C ++, Name lookup is a process of finding the corresponding statement through name. For a function, name
(milliseconds)]=datediff (Ms,@d,getdate ())12. Description: Several advanced query operation wordsA:union operatorThe UNION operator derives a result table by combining the other two result tables (for example, TABLE1 and TABLE2) and eliminating any duplicate rows in the table. When all is used with the Union (that is, union ALL), duplicate rows are not eliminated. In both cases, each row of the derived table is either from TABLE1 or from TABLE2.B:except operatorThe EXCEPT operator derives a re
parameters is not visible in the derived class, which is the name hiding.name hiding is independent of virtual function . so regardless of whether the two functions in the base class are virtual functions, name hiding occurs here . There are two solutions. The first one is to change the MethodA of the 2 parameters to a name, which is visible in the derived class
We conclude this miniseries by considering some implications of the interface principle on Name Lookup. Can you spot the (quite subtle) problem lurking in the following code?
What is name hiding? Show how it can affect the visibility of base class names in Derived classes.
Will the following example compile correctly? Make your answer as complete as you can.
1, the introduction of the problem1). Observe the following first block of code:#include This code compiles with no errors ..... ..... 2). Look at the following second block of code:#include There was an error compiling this code .... 3). Then look at the third block of code:#include This code compiles without errors ..... 4). Fourth Block code:#include there is no error in compiling this code ......... ..... 5). Fifth Block Code:#include error compiling this code ..... 2. DiscoveryDiscovery 1:
Difficulty: 9 bytes
When you call a function, which function do you call? The answer is determined by Name Lookup, But you're almost certain to find some of the details surprising.
In the following code, which functions are called? Why? Analyze the implications.
namespace A { struct X; struct Y; void f( int ); void g( X );}namespace B{ void f( int i ) { f( i ); // which f()? } void g( A::X x )
/wKiom1c9uZjSt1iNAAAlcAA8om0578.png "title=" 16.PNG "alt=" Wkiom1c9uzjst1inaaalcaa8om0578.png "/>Third, the special function of findThe special function of find is to be able to perform additional actions (action).650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M01/80/4F/wKioL1c9v7iTc3uVAAA7ZgrNX1w161.png "title=" Capture 1. PNG "alt=" Wkiol1c9v7itc3uvaaa7zgrnx1w161.png "/>Find not only can specify the directory to find (along with subdirectories), but can also use additional parameters t
The definition of overloaded functions: several functions within the same scope have the same name but different parameter lists, called overloaded functions. Here is an important premise: the same scope;If the overloaded function is defined in a different scope, then once the compiler finds the desired name in the current scope, the compiler ignores the entity with the same
The cause of the problem is that the page on the WordPress background is slow or even unresponsive in the local environment, excluding the Google font or the reference of third-party ajax, the page prompts "an unexpected error may occur in WordPress.org or the server configuration file". The debug program returns name lookup timed out and reports an error.For example, when these two pages are open
This is an area I have never known since I learned C ++. Recently I want to review the basic knowledge of C ++, so I am reading a book. I think this part about name search is novel in this book. I will summarize it a little.
What is name search?
In my opinion, it should be like this. For example, if you call a function, how does the compiler look for the definition of this function. This is the so-called
An important work of the compiler is to parse the name it encounters, in general, the compiler is in order to parse the name encountered, for example, the compiler encountered a function, then will generate code for this function, but if the function called another function, and this function has not been parsed, Then the compiler will make an error, such as the following example:void H () {f ();} void F ()
IP lookup domain name PHP source code. IP lookup domain names, usually bing's IP query function is used now, that is, IP: 222.222.222.222 is written as php code? Php call method $ resultgetResult (124.205.228.114); print _ IP lookup domain name, usually using an IP address q
Basic Principles of database connection pool technology:
A data source object is provided by a Web Container (such as Tomcat ).ProgramUsing the JNDI technology to obtain this object. Generally, If you create a connection by yourself, use the followingCodeGet the data source object:
Context context = new initialcontext ();
Datasource = (datasource) Context. Lookup ("Java://COMP/ENV/jdbc/mydb ");
Connection conn = datasource. getconnection ();
template y still inherits from X, and "G ()" in f () in Y, then the same g () is called in both ways? The answer is: No, the first method calls the global G (), and the second method calls the base class G (), because when the compiler encounters the first method of G (), it is found that it does not appear to rely on the template parameters, so it is not dependent on the template parameters, so in the first phase of the parsing, at this time X void G () {coutThe result is that the G () of the
Write a program that finds files in the current directory and all subdirectories of the current directory that contain the specified string and prints out the absolute path.
Import OS class Searchfile (object): Def __init__ (self,path= '. '): Self._path=path Self.abspath=os.pat H.abspath (self._path) # Default current directory Def findfile (self,keyword,root): filelist=[] for root,dirs,files in OS . Walk (Root): for name in Files:fitfile=filelist.ap
Difficulty: 5
Take a few minutes to consider some implications of the interface principle on the way we reason about Program Design. We'll revisit a classic design problem: "What's the best way to writeOperator ? "
There are two main ways to writeOperator For a class: As a free function that uses only the usual interface of the class (and possibly accessing nonpublic parts directly asFriend), Or as a free function that callaVirtual print ()Helper function in the class.
Which method is better? Wh
By default, make will look for the makefile file to read and execute in the file name order in the working directory (the directory where the make is executed), looking for the file name in the following order: "Gnumakefile", "Makefile", "makefile".Usually you should use "makefile" or "makefile" as a Makefile file name (we recommend using "Makefile", capitalized
1. File name LookupWhen using the Find query, because the disk query, so slow, so the Linux query more often use which, whereis, locate to query, because it is the use of database queries, so fast.2. WhichOur common ls command, if we want to know where these common commands are placed, use the which command to query the address. which uses the PATH environment variable to find the file name, WHICH-A returns
Domain Name Lookup by IP address, which is usually an IP address query function of bing, that is, IP Address: 222.222.222.222Writing php code becomes// Call Method$ Result = getResult ("124.205.228.114 ");Print_r ($ result );Function getContent ($ url ){$ Content = file_get_contents ($ url );Return $ content;}Function getResult ($ ip ){$ Pagesize = 10;$ Page = 1;$ Url = "http://cn.bing.com/search? Q = ip %
View the error prompt in the system log as
2014/09/19 18:06:55 [4696] name lookup failed for 212.173.9.32:no address associated with hostname
The solution is because the main rsync configuration file does not have access to IP settings so access is denied.
Find the rsyncd.conf file in your installation directory
Hosts allow = Your IP address is like this
And then you can save it.
Summary, today made a
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