Hi there,
I was surprised by this behavior, but it's entirely possible there's a good
reason for it. Bringing it up to understand what that might be. In using
(in-set) or (in-mutable-set) in a for loop, it seems that if the loop is
removing and adding elements to the set it is iterating over, the sequence
might terminate even if the set is non-empty.
Example:
(let ([my-set (mutable-set 0)])
(for ([i (in-mutable-set my-set)])
(printf "~a\n" i)
(when (= i 0)
(set-remove! my-set i)
(set-add! my-set 1))))
Outputs:
>
0
Instead of the expected:
>
0
1
Changing the code to remove the (set-remove! my-set i) line:
(let ([my-set (mutable-set 0)])
(for ([i (in-mutable-set my-set)])
(printf "~a\n" i)
(when (= i 0)
(set-add! my-set 1))))
... produces the expected output.
On a related note, I'm not exactly clear on what a sequence is that isn't a
stream or a list or some other concrete type. Sequences appear to be an
abstract type, and yet (in-set) is an instance of it (unlike e.g. (in-list)
which is a stream..) so it must not be abstract. Perhaps this is the key to
my confusion here?
Thanks,
-Sid
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