Your pseudo-code is pretty much correct. For this example, suppose we had a method call foo.bar() where foo: T. I’m going to use the fully qualified syntax (FQS) to be unambiguous about what type the method is being called with, e.g. A::bar(foo) or A::bar(&***foo). I’m just going to write a pile of random capital letters, … Read more
Yes, it’s subassignment in R using <- (or = or ->) that makes a copy of the whole object. You can trace that using tracemem(DT) and .Internal(inspect(DT)), as below. The data.table features := and set() assign by reference to whatever object they are passed. So if that object was previously copied (by a subassigning <- … Read more
The thread support in the standard library allows the created threads to outlive the thread that created them; that’s a good thing! However, if you were to pass a reference to a stack-allocated variable to one of these threads, there’s no guarantee that the variable will still be valid by the time the thread executes. … Read more
(Just to be clear, the explanation I’m giving here is specific to Java and C#. Don’t assume it applies to other languages, although bits of it may.) I like to use an analogy of telling someone where I live. I might write my address on a piece of paper: A variable is like a piece … Read more
Well, the onclick property expects a reference to a function, for it to execute when the element is clicked. Normally it’s either: element.onclick = funcRef; or element.onclick = function () { funcRef(); }; (but of course, it’s best to use addEventListener and attachEvent) Notice how both of them are references to functions, not calling. When … Read more
This is more an art than a science. The Mongo Documentation on Schemas is a good reference, but here are some things to consider: Put as much in as possible The joy of a Document database is that it eliminates lots of Joins. Your first instinct should be to place as much in a single … Read more
Python never implicitly copies objects. When you set dict2 = dict1, you are making them refer to the same exact dict object, so when you mutate it, all references to it keep referring to the object in its current state. If you want to copy the dict (which is rare), you have to do so … Read more
From this Visual C++ blog article about rvalue references: … C++ doesn’t want you to accidentally modify temporaries, but directly calling a non-const member function on a modifiable rvalue is explicit, so it’s allowed … Basically, you shouldn’t try to modify temporaries for the very reason that they are temporary objects and will die any … Read more
The question you asked TL;DR: No, you cannot return a reference to a variable that is owned by a function. This applies if you created the variable or if you took ownership of the variable as a function argument. Solutions Instead of trying to return a reference, return an owned object. String instead of &str, … Read more
TL;DR: One can instead use &str, &[T] or &T to allow for more generic code. One of the main reasons to use a String or a Vec is because they allow increasing or decreasing the capacity. However, when you accept an immutable reference, you cannot use any of those interesting methods on the Vec or … Read more