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Multiline strings in JSON
... control characters. As an additional example to make it more clear, consider that "\\" is an escape sequence for backslash, as opposed to a literal backslash. The JSON grammar explicitly excludes control characters (cf. the "char" definition), and instead provides for their representation via es...
How to map with index in Ruby?
...1.9, you can use the fact that iterator methods like each_with_index, when called without a block, return an Enumerator object, which you can call Enumerable methods like map on. So you can do:
arr.each_with_index.map { |x,i| [x, i+2] }
In 1.8.6 you can do:
require 'enumerator'
arr.enum_for(:eac...
get and set in TypeScript
...;
})();
So to use it,
var myFoo = new foo();
if(myFoo.bar) { // calls the getter
myFoo.bar = false; // calls the setter and passes false
}
However, in order to use it at all, you must make sure the TypeScript compiler targets ECMAScript5. If you are running the command line compil...
Is the C# static constructor thread safe?
... {
mutex.WaitOne();
return instance;
}
// Each call to Acquire() requires a call to Release()
public static void Release()
{
mutex.ReleaseMutex();
}
}
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Django - filtering on foreign key properties
...
student_user = User.objects.get(id=user_id)
available_subjects = Subject.objects.exclude(subject_grade__student__user=student_user) # My ans
enrolled_subjects = SubjectGrade.objects.filter(student__user=student_user)
context.update({'available_subjects': av...
Is there a decorator to simply cache function return values?
...(maxsize=100, typed=False)
Decorator to wrap a function with a memoizing callable that saves up to the maxsize most recent calls. It can save time when an expensive or I/O bound function is periodically called with the same arguments.
Example of an LRU cache for computing Fibonacci numbers:
@lr...
Is null check needed before calling instanceof?
...
Specifically, in Item 8, he notes that in equals() methods, one instanceof operator serves two purposes - it verifies that the argument is both non-null and of the correct type. "...[S]o you don't need a separate null check."
...
Overload with different return type in Java?
...e alone is not sufficient for the compiler to figure out which function to call:
public int foo() {...}
public float foo() {..}
...
foo(); // which one?
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try/catch versus throws Exception
...ropagate. (I'm assuming that showException doesn't rethrow it.)
So if you call the first method and "do something" fails, then the caller will have to handle the exception. If you call the second method and "do something" fails, then the caller won't see an exception at all... which is generally a ...
Redirecting Output from within Batch file
...r good and fast way that only opens and positions the file once
@echo off
call :sub >output.txt
exit /b
:sub
command1
command2
...
commandN
Edit 2020-04-17
Every now and then you may want to repeatedly write to two or more files. You might also want different messages on the screen. It is st...