bitwise shift operator not found

[Justin Smith]

fun first1 {ndx:int | ndx >= 1} (ndx: ulint ndx, nzer: ulint): (ulint, ulint) =
if (ndx land 1ul) = 0ul
then first1 ((ndx >> 1ul), nzer + 1ul)
else (ndx, nzer)

the above code gives the following error:

 error(3): the symbol [>>] cannot be resolved as no match is found.

as you can see, I tried to introduce a dependent type, mostly in speculation of the conditions where the compiler would approve of a bit shift, or consider it "safe"

Is there a general overview for bitwise operations in ats2? I haven't been able to find anything in the html book from the main site.

[Brandon Barker]

My understanding is that this sort of low level mechanism might be best left to implementing (possibly inline) in C:

http://www.ats-lang.org/DOCUMENT/INT2PROGINATS/HTML/c1995.html

Brandon Barker
brandon...@gmail.com

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[gmhwxi]

ndx >> 1ul

should be

ndx >> 1

However, the typechecker does not know that ndx >> 1 yields a nonzero integer in this case. So you
will encounter a type-error.

[gmhwxi]

This version typechecks:

fun
first1{i:pos}
(
  ndx: ulint(i), nzer: uint
) : (ulint, uint) =
(
if
iseqz (ndx land 1ul)
then let
  val ndx = ndx >> 1
  val [i:int] ndx = g1ofg0 (ndx)
  prval () = __assert () where
  {
    extern praxi __assert (): [i >= 1] void
  }
in
  first1 (ndx, succ(nzer))
end // end of [then]
else (ndx, nzer) // end of [else]
) (* end of [first1] *)

On Tuesday, June 24, 2014 1:10:18 PM UTC-4, Justin Smith wrote: