Hi Artyom,
I'm also grappling with the issue of RT in this case as I'd so far only
thought about it in terms of function calls, but what you and Vanessa say
helped me to understand the issue. Though I haven't managed to get ATS to
have the same behavior as OCaml in the "let expression" above, I suspect it
is possible. The key phrase here seems to be "side-effecting expression",
and relates to the fact that functions in ATS can perform side effects
without having any effect type or IO monad ascribed to the value (again,
iirc).
Perhaps tonight I should try out the same in Idris or PureScript, which are
not lazily evaluated by default but do use IO, to get a better
understanding.
On Thursday, March 21, 2019 at 3:17:46 AM UTC-4, Artyom Shalkhakov wrote:
>
> Hi Brandon,
>
> Admittedly I don't really understand what RT is, but from what I
> understand, in Haskell the expression like [print "ha"] is basically a
> command to the top-level interpreter (which is the language runtime) to
> perform an effect on the console (moreover, it will be evaluated on
> as-needed basis). Moreover, the ";" is itself another comand, the explicit
> sequencing command, the meaning of which is "perform the left-hand side
> effects, then perform the right-hand side effects". Such a command is a
> value, so it can be passed as a value and reused as many times as is
> necessary. In ATS, the expression like [print "ha"] evaluates right there
> to a void/"no value", and the ";" is also NOT a value at all, but rather a
> "shortcut" syntax to a "let-in-end" form.
>
> I like to imagine an interpreter that sits in the Haskell's runtime.
> Values of IO type are commands to this interpreter. Typical Haskell
> IO-based programs are building up these commands as they are being
> evaluated by the runtime. The runtime starts evaluation at the "main"
> expression defined by the programmer.
>
> чт, 21 мар. 2019 г. в 03:45, Brandon Barker <brandon...@gmail.com
> <javascript:>>:
>
>> I'm a little rusty, so can't come up with many good examples.
>>
>> Apparently it is possible to do something like this in OCaml:
>>
>> implement
>> main0 () = {
>> val () = let
>> val ha = print("ha")
>> in
>> (ha; ha) // How to get two ha's here?
>> end
>> }
>>
>>
>> After running the program, you would only see one "ha", which violates RT.
>>
>> However, ATS doesn't seem to allow a sequence expression in the "in"
>> position of a let expression, as this doesn't compile. Admittedly I'm just
>> trying to see if ATS2 doesn't have RT in this particular case, but it would
>> also be good to know about the sequence expressions here.
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "ats-lang-users" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to ats-lang-user...@googlegroups.com <javascript:>.
>> To post to this group, send email to ats-lan...@googlegroups.com
>> <javascript:>.
>> Visit this group at https://groups.google.com/group/ats-lang-users.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/ats-lang-users/5eba6b86-4146-4ba2-a87f-f8c511d902f0%40googlegroups.com
>>
>> <https://groups.google.com/d/msgid/ats-lang-users/5eba6b86-4146-4ba2-a87f-f8c511d902f0%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
>
> --
> Cheers,
> Artyom Shalkhakov
>
--
You received this message because you are subscribed to the Google Groups
"ats-lang-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to ats-lang-users+unsubscr...@googlegroups.com.
To post to this group, send email to ats-lang-users@googlegroups.com.
Visit this group at https://groups.google.com/group/ats-lang-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/ats-lang-users/b1765d06-7659-4a60-846f-25535e87a0b9%40googlegroups.com.
