[R] return value of {....}

Leonard Mada
2023-01-12T20:14:45Z

Dear Akshay,

The best response was given by Andrew. "{...}" is not a closure.

This is unusual for someone used to C-type languages. But I will try to
explain some of the rationale.

In the case that "{...}" was a closure, then external variables would
need to be explicitly declared before the closure (in order to reuse
those values):
intermediate = c()
{
 ??? intermediate = ...;
 ??? result = someFUN(intermediate);
}

1.) Interactive Sessions
This is cumbersome in interactive sessions. For example: you often
compute the mean or the variance as intermediary results, and will need
them later on as well. They could have been computed outside the
"closure", but writing code in interactive sessions may not always be
straightforward.

2.) Missing arguments
f = function(x, y) {
 ??? if(missing(y)) {
 ?? ?? ? # assuming x = matrix
 ??? ??? y = x[,2]; x = x[,1];
 ??? }
}
It would be much more cumbersome to define/use a temporary tempY.

I hope this gives a better perspective why this is indeed a useful
feature - even if it is counterintuitive.

Sincerely,

Leonard