> Depending on other design decisions, it make make sense to consider
> this an IDE issue. That is, maybe the best thing is to have some kind
> of interactive value in the REPL that lets the user have control over
> the effects. (And this doesn't just have to be via some kind of
> simplistic mouse clicking -- I think there is a lot of unexplored UI
> space here).
I'd definitely be curious to see what you have in mind beyond some "simplistic
mouse clicking". It would be cool to convey more information about sequence
values via DrRacket's capability to render snips.
As for Daniel's point about the contract violation, I've pushed a change that
makes `sequence?` into a custom flat contract, so that example now gives a more
useful error message:
> (take 5 (list->vector (range 10)))
take: contract violation
expected: (and/c immutable? sequence?)
given: '#(0 1 2 3 4 5 6 7 8 9), which is mutable
However, this only works when the contract is used alone in a first-order way.
It doesn't give a helpful error message when used with `first`, for example:
> (first (vector 0))
first: contract violation
expected: (and/c sequence? (not/c empty?))
given: '#(0)
which isn't: sequence?
It would be possible in this case, of course, to create a `nonempty-sequence?`
contract, but it still wouldn't work in other cases. Robby, do you know of any
way I could provide this extra error reporting in more cases while still
keeping `sequence?` a flat contract?
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