Use: : to detect the function, and assign to it if it does not exist.
使用：来检测这个函数，如果不存在就赋值上这个函数。
And if it does not exist, then existing theories of physics will have to be scrapped.
而如果它不存在，那么现有的物理学理论都将废弃。
Shared memory is created if it does not exist, and the shared object is created within it.
如果共享内存尚不存在，就创建共享内存；并在其中创建对象。
A file system path. The file does not have to exist on disk. If it does not exist, it is created for you.
一个系统文件路径，这个文件路径不一定需要存在，如果不存在，它会自动为你创建。
It calls into the application for this functionality and fails if it does not exist or is not implemented properly.
它将调入应用程序来查找该功能，如果该功能不存在或实现有误，则发生失败。
Add (key, value [, expiry]) - Adds the key to the cache if it does not exist or returns an error if the key already exists.
add (key,value [，expiry])—如果键不存在就将这个键添加到缓存内，如果键已经存在就返回错误。
The first command creates the database (if it does not exist already) as well as a table with two columns, an issue number, and a title.
第一个命令创建数据库(如果数据库还不存在的话)和一个表，这个表包含两列——期号和标题。
A project named.hsqldb is created, if it does not exist, and inside it the engine will look for database.script and other database files.
一个名为.hsqldb的项目如果不存在就会被创建，而在该项目中引擎将查找database . script和其他数据库文件。
Now if we want to read from it, the other process needs also to create a memory mapped file, we can use the other static initialize that opens an existing one or creates one if it does not exist.
其它进程如何读取该内存映射文件的内容呢。 一样，我们先创建一个内存映射文件。
If the reference that the conditional block will use for input does not exist, create it (as explained in the article on adding dynamic data to your Web service tests in the Resources section).
如果条件块为了输入而使用的引用不存在，那么就创建它(这在参考资料部分的文章addingdynamicdatatoyourWebservicetests中有解释)。
If the port type does not exist in the target WSDL, the engine creates it with the target WSDL target namespace.
如果该端口类型在目标WSDL中不存在，那么该引擎用目标WSDL的目标命名空间来创建它。
If the file does not exist, the installation application creates it.
如果此文件不存在，安装程序会创建它。
Often, due to development timeline pressure, documentation might not exist, or, if it does exist, it might not be in synchronization with the physical data model in production.
通常，由于开发时间的压力，可能未创建文档，或者即使创建了文档，该文档也可能与生产的物理数据模型不同步。
There’s plenty in “The Grand Design” that, if you are not a physicist or a mathematician, will sometimes hurt your head, especially the ideas about why time as we know it does not exist.
如果你不是一名物理学家或者数学家，《伟大设计》中有很多内容都会让你头大，尤其是些关于众所周知的时间却并不存在的观点。
Even if a personalization requirement does not exist, consider using this approach anyway because it makes adding new functionality and making changes easier in the future.
甚至在不要求个性化的情况下您也可以考虑使用这种方法，因为它在以后可以更加方便是添加新功能和进行修改。
"If the effect really does exist, it would appear to me that it would not be difficult to use it in a clinical setting," he says.
他还说：“若是该效应真正存在，那么对于我而言，这将不难将其应用在临床环境之中。”
The second method accepts a boolean argument that determines whether or not a new Session will be created if it does not yet exist.
第二个方法接受一个布尔参数，这个参数用于判定会话不存在时是否创建新会话。
Because we're not passing a full path, this will be created as a subdirectory of the current working directory (if it does not already exist).
因为我们没有传递完整的路径，所以它会在当前目录下创建一个子目录(如果它还不存在的话)。
If a service has to be developed (if it does not already exist), then the software architect should consider submitting (publishing) it to the enterprise's service registry.
如果必须开发服务(如果不存在)，则软件架构师应考虑将其提交(发布)到企业的服务注册中心。
After all, I think, if Heaven does exist it’s likely that I’ll enter it with just such a flock of sheep, of people—old, not all that smart, a bit greedy.
总之，我想，如果天堂确实存在的话，我就可能会和这群羊，这群人（年老的，有点贪心的，并非都很时髦的）一道进去。
If a file in the partial application does not exist in the deployed application EAR, then it is added to the deployed EAR file as a result of update operation.
如果部分应用程序中的文件不存在于已部署的应用程序EAR中，则更新操作会将其添加到已部署的EAR文件。
Import the ca root certificate, if it does not already exist in the trust store of the client or the server.
如果客户端或服务器的信任存储区中尚没有ca根证书，则导入该证书。
IF the session object does not exist, SIF creates a new security context and puts it in the security context holder.
如果不存在会话对象，SIF将创建一个新的安全上下文，并将它放到securitycontext holder中。
If the database does not exist, MongoDB will create it as soon as you add any data to it.
如果数据库不存在，在您将数据添加到数据库时，MongoDB将会创建它。
If the Windows user does not exist, it generates an output message in the results window and then manually creates the login after it first adds the Windows user.
如果该Windows用户不存在，则将在结果窗口中生成一条输出消息，然后在它首次添加该Windows用户后手动创建登录。
If the postcard queue does not exist on your system, you can either create it or change the destination queue to one that already exists.
如果您的系统上没有postcard队列，您可以创建一个postcard队列，或者将目标队列更改为一个已经存在的队列。
The first snippet in Listing 1 shows the common put-if-absent idiom -- if an entry does not already exist in the Map, add it.
清单1中第一片段展示了公用的put-if-absent语句块――如果一个条目不在Map 中，那么添加这个条目。
The first snippet in Listing 1 shows the common put-if-absent idiom -- if an entry does not already exist in the Map, add it.
清单1中第一片段展示了公用的put-if-absent语句块――如果一个条目不在Map 中，那么添加这个条目。
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