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Regex empty string or email
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This regex pattern will match an empty string:
^$
And this will match (crudely) an email or an empty string:
(^$|^.*@.*\..*$)
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How to declare a type as nullable in TypeScript?
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All fields in JavaScript (and in TypeScript) can have the value null or undefined.
You can make the field optional which is different from nullable.
interface Employee1 {
name: string;
salary: number;
}
var a: Employee1 = { name: 'Bob', sal...
Switch statement multiple cases in JavaScript
...one feature of switch ... case. It's too easy to forget a break statement, and if you use fall through intentionally, those forgotten break statements can be very hard to spot. This method lookup version also has lots of great features that switch ... case lacks, such as dynamic extensibility, or t...
Object of custom type as dictionary key
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You need to add 2 methods, note __hash__ and __eq__:
class MyThing:
def __init__(self,name,location,length):
self.name = name
self.location = location
self.length = length
def __hash__(self):
return hash((self.name, self.lo...
When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?
...cit conversions between types (such as int to float, or pointer to void*), and it can also call explicit conversion functions (or implicit ones). In many cases, explicitly stating static_cast isn't necessary, but it's important to note that the T(something) syntax is equivalent to (T)something and s...
How can I decompress a gzip stream with zlib?
... a bad stream format. By default, zlib creates streams with a zlib header, and on inflate does not recognise the different gzip header unless you tell it so. Although this is documented starting in version 1.2.1 of the zlib.h header file, it is not in the zlib manual. From the header file:
windo...
“Failed to load platform plugin ”xcb“ ” while launching qt5 app on linux without qt installed
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shows that xcb depends on libQt5DBus.so.5 in addition to libQt5Core.so.5 and libQt5Gui.so.5 (and many other system libs). Add libQt5DBus.so.5 to your collection of shared libs and you should be ready to move on.
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python list by value not by reference [duplicate]
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what is the difference between a regular copy and a deep copy? Why does what happens above happen? I think I have a general understanding, it seems to be like the same problem encountered by the op at the second layer. How does it work internally?
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UILabel text margin [duplicate]
I'm looking to set the left inset/margin of a UILabel and can't find a method to do so. The label has a background set so just changing its origin won't do the trick. It would be ideal to inset the text by 10px or so on the left hand side.
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How to make PyCharm always show line numbers
...g to enable line numbers for all files, but I have to always right click and enable this on per file basis.
6 Answers
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