FWIW, I personally would use FILEptr_is_null to check if fptr is null, rather than ptrcast and then a comparison to 0
On 3/12/19 2:22 PM, Hongwei Xi wrote:
> Here is a quick fix:
> extern
> praxi
> clear{a:t0ype}(x: INV(a)): void
>
> fun open_close(): void =
> let
> val fptr = fopen("hello.dats", file_mode_r)
> val p = ptrcast(fptr)
> in
> if p = 0
> then
> let
> prval () = FILEptr_free_null(fptr)
> in
> end
> else
> let
> val (pf|rc) = fclose(fptr)
> val () = assertloc(rc = 0) // fclose is expected to succeed
> prval None_v() = pf
> prval () = clear(fptr)
> in
> end
> end
>
> ######
>
> The above shows a C-style of dealing with IO in ATS. What I like to
> recommend
> is to deal with IO via the use of linear streams:
>
> https://github.com/ats-lang/ATS-CodeBook/tree/master/RECIPE/ReadFromSTDIN
>
> On Tue, Mar 12, 2019 at 2:17 PM Shimin Guo <smguo2...@gmail.com
> <mailto:smguo2...@gmail.com>> wrote:
>
> I wrote the following code
>
> |
> #include "share/atspre_define.hats"
> #include "share/atspre_staload.hats"
>
> staload "libats/libc/SATS/stdio.sats"
>
> fun open_close(): void =
> let
> val fptr = fopen("hello.dats", file_mode_r)
> val p = ptrcast(fptr)
> in
> if p = 0
> then
> let
> prval () = FILEptr_free_null(fptr)
> in
> end
> else
> let
> val (pf|rc) = fclose(fptr)
> val () = assertloc(rc = 0) // fclose is expected to succeed
> prval None_v() = pf
> in
> end
> end
>
> |
>
>
> and got the following compiler error:
>
>
> /home/sguo/ats/file.dats: 242(line=13, offs=7) -- 307(line=16,
> offs=10): error(3): the dynamic variable [fptr$4718(-1)] is
> consumed but it should be retained with the type
> [S2Eapp(S2Ecst(ptr_addr_type); S2Evar(l$8617$8618(14269)))] instead.
> patsopt(TRANS3): there are [1] errors in total.
> exit(ATS): uncaught exception:
>
> _2home_2hwxi_2Research_2ATS_2dPostiats_2src_2pats_error_2esats__FatalErrorExn(1025)
>
>
>
> Why does it say fptr should be retained?
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