reference

Array.fill(Array) creates copies by references not by value [duplicate]

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You could use Array.from() instead: Thanks to Pranav C Balan in the comments for the suggestion on further improving this. let m = Array.from({length: 6}, e => Array(12).fill(0)); m[0][0] = 1; console.log(m[0][0]); // Expecting 1 console.log(m[0][1]); // Expecting 0 console.log(m[1][0]); // Expecting 0 Original Statement (Better optimized above): let m = Array.from({length: 6}, e => … Read more

What is the return type of the built-in assignment operator?

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The standard correctly defines the return type of an assignment operator. Actually, the assignment operation itself doesn’t depend on the return value – that’s why the return type isn’t straightforward to understanding. The return type is important for chaining operations. Consider the following construction: a = b = c;. This should be equal to a … Read more

Is there a generic way for a function to reference itself?

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There is no generic way for a function to refer to itself. Consider using a decorator instead. If all you want as you indicated was to print information about the function that can be done easily with a decorator: from functools import wraps def showinfo(f): @wraps(f) def wrapper(*args, **kwds): print(f.__name__, f.__hash__) return f(*args, **kwds) return … Read more

How to set the default of a JSONField to empty list in Django and django-jsonfield?

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According to the Django documentation for JSONField you should indeed use default=list because using default=[] would create a mutable object that is shared between all instances of your field and could lead to some objects not having an empty list as a default. Please note that this does not only apply for django.contrib.postgres.fields.JSONField but for … Read more

What are the reference collapsing rules, and how are they utilized by the C++ standard library?

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The reference collapsing rules (save for A& & -> A&, which is C++98/03) exist for one reason: to allow perfect forwarding to work. “Perfect” forwarding means to effectively forward parameters as if the user had called the function directly (minus elision, which is broken by forwarding). There are three kinds of values the user could … Read more

What is the advantage of std::ref and std::reference_wrapper compared to regular references?

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Well ref constructs an object of the appropriate reference_wrapper type to hold a reference to an object. Which means when you apply: auto r = ref(x); This returns a reference_wrapper and not a direct reference to x (ie T&). This reference_wrapper (ie r) instead holds T&. A reference_wrapper is very useful when you want to … Read more