Carlos Aya wrote:
>Just curious if you have among the plans, implementation of so-called observer
>types, i.e. variables that do not add as counting occurences.
Clean already observer references, see section 9.4 of the reference manual.
For example, size can be used in a guard or in a #! as an observer.
>The problem with the following function ...
>
>doIt :: *(a e) (Int -> e) -> *(a e) | Array a e
>doIt arr f = {arr & [i] = f i \\ i <- [0.. (size arr)]}
>
>... is that (size arr) counts as occurrence in the body of doIt, so arr cannot
>be unique. But as seen in the _SystemArray implementation, size only reads the
>size of the array which we know is fixed. So, truly its signature should be
>
>size :: 0:arr -> Int
>
>(I put 0: to indicate an "observed" parameter, out of my ignorance.. and based
>on Odersky paper...)
This should work:
doIt arr f
#! s = size arr
= {arr & [i] = f i \\ i <- [0.. s-1]}
or you could use usize instead:
doIt arr f
# (s,arr) = usize arr
= {arr & [i] = f i \\ i <- [0.. s-1]}
Kind regards,
John van Groningen
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