The support for type inference in ATS2 is weak.
Often you need a type annotation for a case-expression
(or an if-expression):
implement main0() = {
val a = 0
val b =
(
case+ a of
| 0 => Some_vt(0) *(* 9 *)*
| _ => None_vt() *(* 10 *)*
) : Option_vt(int)
val () =
case+ b of
| ~None_vt() => ()
| ~Some_vt(_) => ()
}
On Tue, Oct 13, 2020 at 10:09 AM Dambaev Alexander <ice.redm...@gmail.com>
wrote:
> Hi,
>
> In this example, I am trying to define a binding of type Option_vt(int),
>
> ```
> #include "share/atspre_staload.hats"
>
> #define ATS_DYNLOADFLAG 0
>
> implement main0() = {
> val a = 0
> val b =
> case+ a of
> | 0 => Some_vt(0) *(* 9 *)*
> | _ => None_vt() *(* 10 *)*
> val () =
> case+ b of
> | ~None_vt() => ()
> | ~Some_vt(_) => ()
> }
> ```
> but I get the following error from the compiler:
> ```
> patscc -O2 -DATS_MEMALLOC_LIBC -I"../libs/" -o issue main.dats
> /data/devel/ats2/issue/main.dats: 136(line=9, offs=12) -- 146(line=9,
> offs=22): error(3): the dynamic expression cannot be assigned the type
> [S2EVar(5243)].
> /data/devel/ats2/issue/main.dats: 136(line=9, offs=12) -- 146(line=9,
> offs=22): error(3): mismatch of sorts in unification:
> The sort of variable is: S2RTbas(S2RTBASimp(1; t@ype))
> The sort of solution is: S2RTbas(S2RTBASimp(2; viewtype))
> /data/devel/ats2/issue/main.dats: 136(line=9, offs=12) -- 146(line=9,
> offs=22): error(3): mismatch of static terms (tyleq):
> The actual term is: S2Eapp(S2Ecst(option_vt0ype_bool_vtype);
> S2Eapp(S2Ecst(g1int_int_t0ype); S2Eextkind(atstype_int), S2Eintinf(0)),
> S2Ecst(true_bool))
> The needed term is: S2EVar(5243)
> /data/devel/ats2/issue/main.dats: 158(line=10, offs=12) -- 167(line=10,
> offs=21): error(3): the dynamic expression cannot be assigned the type
> [S2EVar(5243)].
> /data/devel/ats2/issue/main.dats: 158(line=10, offs=12) -- 167(line=10,
> offs=21): error(3): mismatch of sorts in unification:
> The sort of variable is: S2RTbas(S2RTBASimp(1; t@ype))
> The sort of solution is: S2RTbas(S2RTBASimp(2; viewtype))
> /data/devel/ats2/issue/main.dats: 158(line=10, offs=12) -- 167(line=10,
> offs=21): error(3): mismatch of static terms (tyleq):
> The actual term is: S2Eapp(S2Ecst(option_vt0ype_bool_vtype); S2EVar(5245),
> S2Ecst(false_bool))
> The needed term is: S2EVar(5243)
> /data/devel/ats2/issue/main.dats: 200(line=13, offs=7) -- 210(line=13,
> offs=17): error(3): the constructor pattern cannot be assigned the type
> [S2EVar(5243)].
> /data/devel/ats2/issue/main.dats: 223(line=14, offs=7) -- 234(line=14,
> offs=18): error(3): the constructor pattern cannot be assigned the type
> [S2EVar(5243)].
> ```
> what is wrong with this example?
>
> Instead, this example is working:
> ```
> #include "share/atspre_staload.hats"
>
> #define ATS_DYNLOADFLAG 0
>
> implement main0() = {
> val a = 0
> val b =
> * f(a) where { fn f(a:int):<> Option_vt(int) =*
> case+ a of
> | 0 => Some_vt(0)
> | _ => None_vt()
> }
> val () =
> case+ b of
> | ~None_vt() => ()
> | ~Some_vt(_) => ()
> ```
> I have tried to reread the tutorial, but haven't found something related
> to this behavior
>
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