[stream_vt_head_exn], strange behavior

[August Alm]

Hi!

The following code compiles but segfaults when run:

         val from_vt_nine = from_vt(9)
         val nine = stream_vt_head_exn<int>(from_vt_nine)
         val () = println!(nine: int)

The follwing code, on the other hand, executes as expected:

         val from_vt_nine = from_vt(9)
         val- ~stream_vt_cons(nine, ns) = !from_vt_nine
         val () = println!(nine: int)

Both examples prefaced with

         #include "share/atspre_define.hats"
         #include "share/atspre_staload.hats"
        
         val from_vt = fix f(i: int): stream_vt(int) =>
           $ldelay( stream_vt_cons{int}(i, f(i+1))
                     , ~f(i) )

What's up with this?

[Hongwei Xi]

The 'free' part of from_vt should be dropped:

val
from_vt =
fix f(i: int): stream_vt(int) =>

$ldelay(stream_vt_cons{int}(i, f(i+1)))

stream_vt_head_exn tries to free a given stream. In the above case,

freeing the given stream trigger infinite computation.

In the follow code, 'ns' is leaked:

val from_vt_nine = from_vt(9)
val- ~stream_vt_cons(nine, ns) = !from_vt_nine
val () = println!(nine: int)

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[August Alm]

Thank you! Still learning how to handle laziness. =)

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[gmhwxi]

stream_vt is pretty similar to the linear hom you used.
Essentially, stream_vt is a linear hom whose arity equals 0.