The assignment operator in Java evaluates to the assigned value (like it does in, e.g., c). So here, readLine() will be executed, and its return value stored in line. That stored value is then checked against null, and if it’s null then the loop will terminate.
Update of 2018-10-10: The most succinct way to carry out this specific task is to use list2env() like so: ## Create an example list of five data.frames df <- data.frame(x = rnorm(25), g = rep(factor(LETTERS[1:5]), 5)) LIST <- split(df, df$g) ## Assign them to the global environment list2env(LIST, envir = .GlobalEnv) ## Check that it … Read more
The way you describe it is absolutely not possible. Assignment to a name is a fundamental feature of Python and no hooks have been provided to change its behavior. However, assignment to a member in a class instance can be controlled as you want, by overriding .__setattr__(). class MyClass(object): def __init__(self, x): self.x = x … Read more
It’s not deprecated and is unlikely to be. It’s the standard way to, for example, make part of one array or object mirror changes made to another, instead of copying the existing data. It’s called assignment by reference, which, to quote the manual, “means that both variables end up pointing at the same data, and … Read more
Strictly speaking, the result of a copy assignment operator doesn’t need to return a reference, though to mimic the default behavior the C++ compiler uses, it should return a non-const reference to the object that is assigned to (an implicitly generated copy assignment operator will return a non-const reference – C++03: 12.8/10). I’ve seen a … Read more
In PL/PgSQL parser, assignment operator is defined as assign_operator : ‘=’ | COLON_EQUALS ; This is a legacy feature, present in source code since 1998, when it was introduced – as we can see in the PostgreSQL Git repo. Starting from version 9.4 it is oficially documented. This idiosyncrasy – of having two operators for … Read more
As David Arenburg mentions in a comment, the answer can be found here. There was a bug fixed in the version 1.9.6 but the fix introduced this downside. One should call DT[] at the end of the function to prevent this behaviour. myfunction <- function(dt) { dt[, z := y – x][] } myfunction(mydt) # … Read more
No, it is not valid C and has never been valid C. These examples are so-called constraint violations of the standard. The standard does not allow you to initialize/assign a pointer to an integer, nor an integer to a pointer. You need to manually force a type conversion with a cast: int* p = (int*) … Read more
In an assignment statement, the right-hand side is always evaluated fully before doing the actual setting of variables. So, x, y = y, x + y evaluates y (let’s call the result ham), evaluates x + y (call that spam), then sets x to ham and y to spam. I.e., it’s like ham = y … Read more
= is the assignment operator. It sets a variable (the left-hand side) to a value (the right-hand side). The result is the value on the right-hand side. == is the comparison operator. It will only return true if both values are equivalent after coercing their types to the same type. === is a more strict … Read more