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What is 'Pattern Matching' in functional languages?
...a functional language, the datatypes that you define are usually what are known as discriminated unions or algebraic data types. For instance, what's a (linked) list? A linked list List of things of some type a is either the empty list Nil or some element of type a Consed onto a List a (a list of...
MongoDB数据导出导入工具：mongoexport,mongoimport - 大数据 & AI - 清泛...
...to lock the data directory, so cannot be used
if a mongod is currently accessing the same path
--directoryperdb if dbpath specified, each db is in a separate
directory
--journal enable journaling
-d [ --db ] ...
What characters are valid for JavaScript variable names?
...t it would be if it weren't for the fact that Unicode escape sequences are now valid in identifiers, too! This is exact according to the ES6 spec: (?:[\p{ID_Start}\$_]|\\u(?:[\dA-Fa-f]{4}|\{[\dA-Fa-f]+\}))([\p{ID_Continue}\$_\u200C\u200D]|\\u(?:[\dA-Fa-f]{4}|\{[\dA-Fa-f]+\}))*
–...
How do I extend a class with c# extension methods?
...
{
public static DateTime Tomorrow
{
get { return DateTime.Now.AddDays(1); }
}
}
Which you would use like this:
DateTime tomorrow = DateTimeHelper.Tomorrow;
share
|
improve t...
Stop pip from failing on single package when installing with requirements.txt
...out the -a flag, consider < requirements.txt xargs -n 1 pip install, or if you don't like the redirect at the front, xargs -n 1 pip install < requirements.txt. :-)
– torek
Jul 6 at 17:21
...
How to manage local vs production settings in Django?
...sed in both, but some of them (like paths to static files) need to remain different, and hence should not be overwritten every time the new code is deployed.
...
[精华]VC++对话框程序打印及打印预览的实现 - C/C++ - 清泛网 - 专注C/C++及内核技术
...
void CMyPrintPreviewDlg::OnButton1()
{
// TODO: Add your control notification handler code here
CMyFrame* pf=new CMyFrame(this);
}
2、增加新类：
用ClassWizard新建CMyFrame类（基类CFrameWnd）,功能上相当于文档/视图的应用程序的框架窗口类
用ClassWizard...
Python: Best way to add to sys.path relative to the current running script
...
If you don't want to edit each file
Install you library like a normal python libray
or
Set PYTHONPATH to your lib
or if you are willing to add a single line to each file, add a import statement at top e.g.
import import_...
Empty set literal?
...
By all means, please use set() to create an empty set.
But, if you want to impress people, tell them that you can create an empty set using literals and * with Python >= 3.5 (see PEP 448) by doing:
>>> s = {*()} # or {*{}} or {*[]}
>>> print(s)
set()
this is b...
Get exception description and stack trace which caused an exception, all as a string
...
See the traceback module, specifically the format_exc() function. Here.
import traceback
try:
raise ValueError
except ValueError:
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb
...