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What is a regular expression which will match a valid domain name without a subdomain?
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Well, it's pretty straightforward a little sneakier than it looks (see comments), given your specific requirements:
/^[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9]\.[a-zA-Z]{2,}$/
But note this will reject a lot of valid domains.
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Can't specify the 'async' modifier on the 'Main' method of a console app
...ember from our intro post that an async method will return to its caller before it is complete. This works perfectly in UI applications (the method just returns to the UI event loop) and ASP.NET applications (the method returns off the thread but keeps the request alive). It doesn't work out so well...
Java 8 NullPointerException in Collectors.toMap
...lue without any problems. Is there a good reason why values cannot be null for Collectors.toMap ?
13 Answers
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What is the most efficient way of finding all the factors of a number in Python?
...rs(n):
return set(reduce(list.__add__,
([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))
This will return all of the factors, very quickly, of a number n.
Why square root as the upper limit?
sqrt(x) * sqrt(x) = x. So if the two factors are the same, they're ...
What is the difference between the GNU Makefile variable assignments =, ?=, := and +=?
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ifeq ($(origin FOO), undefined)
FOO = bar
endif
See the documentation for more details.
Append
VARIABLE += value
Appending the supplied value to the existing value (or setting to that value if the variable didn't exist)
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What characters do I need to escape in XML documents?
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If you use an appropriate class or library, they will do the escaping for you. Many XML issues are caused by string concatenation.
XML escape characters
There are only five:
" "
' '
< &lt;
> &gt;
& &amp;
Escaping characters depends on where...
Mod of negative number is melting my brain
...y position so that it will loop round. Doing i %
arrayLength works fine for positive numbers but for negative numbers it all goes wrong.
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In C/C++ what's the simplest way to reverse the order of bits in a byte?
...s to reverse bit order in a byte, I'm curious as to what is the "simplest" for a developer to implement. And by reversing I mean:
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Why should I care that Java doesn't have reified generics?
... is also fine, the above is just an example, also the try-catch is omitted for brevity)
For all other generic type constructs, the actual type can easily be resolved with a bit help of reflection. The below Q&A illustrate the use cases and possibilities:
Get generic type of java.util.List
How...
What is the purpose of the word 'self'?
...o, or perhaps something yet more different -- but it didn't. Python's all for making things explicit, making it obvious what's what, and although it doesn't do it entirely everywhere, it does do it for instance attributes. That's why assigning to an instance attribute needs to know what instance to...