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MongoDB仿关系型数据库Group聚合例子 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...数据
Dictionary dic = new Dictionary();
dic["_userName"] = ""; // 与原字段名区分开
dic["_date"] = "";
dic["_data"] = "0";
MongoServer server = new MongoClient(MongoConnStr).GetServer();
MongoDatabase db = serve...
How are feature_importances in RandomForestClassifier determined?
...d in [1] (often cited, but unfortunately rarely read...). It is sometimes called "gini importance" or "mean decrease impurity" and is defined as the total decrease in node impurity (weighted by the probability of reaching that node (which is approximated by the proportion of samples reaching that no...
How can you iterate over the elements of an std::tuple?
...rloads for every type the tuple might contain. This works best if you know all the tuple elements will share a common base class or something similar.
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What is the use for Task.FromResult in C#
In C# and TPL ( Task Parallel Library ), the Task class represents an ongoing work that produces a value of type T.
6 Ans...
How to use performSelector:withObject:afterDelay: with primitive types in Cocoa?
The NSObject method performSelector:withObject:afterDelay: allows me to invoke a method on the object with an object argument after a certain time. It cannot be used for methods with a non-object argument (e.g. ints, floats, structs, non-object pointers, etc.).
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Java string to date conversion
...tern seems valid.
Here's an extract of relevance from the javadoc, listing all available format patterns:
Letter Date or Time Component Presentation Examples
------ ---------------------- ------------------ -------------------------------------
G Era designator Text ...
Check if a string is a date value
... is an easy way to check if a value is a valid date, any known date format allowed.
20 Answers
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How to configure Git post commit hook
...it/notifyCommit?url=<URL of the Git repository>
This will scan all the jobs that’s configured to check out the specified URL, and if they are also configured with polling, it’ll immediately trigger the polling (and if that finds a change worth a build, a build will be triggered in tu...
What is the difference between old style and new style classes in Python?
...(x) is always <type
'instance'>.
This reflects the fact that all old-style instances, independently of
their class, are implemented with a single built-in type, called
instance.
New-style classes were introduced in Python 2.2 to unify the concepts of class and type.
A new-s...
Collections.emptyList() vs. new instance
...ntly.
In addition, emptyList() might not create a new object with each call.
Implementations of this method need not create a separate List object for each call. Using this method is likely to have comparable cost to using the like-named field. (Unlike this method, the field does not provide ...