I’m having a little trouble understanding the pass-by-reference properties of data.table. Some operations seem to ‘break’ the reference, and I’d like to understand exactly what’s happening. On creating a data.table from another data.table (via <-, then updating the new table by :=, the original table is also altered. This is expected, as per: ?data.table::copy and … Read more
What are the differences between the assignment operators = and <- in R? I know that operators are slightly different, as this example shows x <- y <- 5 x = y = 5 x = y <- 5 x <- y = 5 # Error in (x <- y) = 5 : could not … Read more
What is this idiom and when should it be used? Which problems does it solve? Does the idiom change when C++11 is used? Although it’s been mentioned in many places, we didn’t have any singular “what is it” question and answer, so here it is. Here is a partial list of places where it was … Read more
What does copying an object mean? What are the copy constructor and the copy assignment operator? When do I need to declare them myself? How can I prevent my objects from being copied? 8 Introduction C++ treats variables of user-defined types with value semantics. This means that objects are implicitly copied in various contexts, and … Read more
Until today, I thought that for example: i += j; Was just a shortcut for: i = i + j; But if we try this: int i = 5; long j = 8; Then i = i + j; will not compile but i += j; will compile fine. Does it mean that in fact … Read more
