[Ur] Need help with desugaring dml

[fold at tuta.io]

Actually, it might be quite simple.Incomplete, but, hopefully, clear example:
table tab : $([Ix = int] ++ someColumns ++ otherColumns) PRIMARY KEY Ix

fun test () : transaction xbody =    <...>    tn <- now;    easy_insert tab ({Ix = ix} ++ field_defaults ++ {Dated = tn});    <...>


11. Feb 2017 22:09 by fold at tuta.io:


>     Sergey,
> Something similar to this:> https://github.com/achlipala/upo/blob/master/sql.ur#L44
> and this:> https://github.com/achlipala/upo/blob/master/sql.ur#L50> might help you a bit.
> Also check other functions in sql.ur
> I believe you also can figure out desugared type expressions from compiler error output if you replace parts of your code with simple expressions of known type.
> https://wiki.haskell.org/GHC/Typed_holes
>
>
>
>
>
> 11. Feb 2017 21:18 by > grrwlf at gmail.com> :
>
>
>> Hi. I'm trying (again) to write an Ur/Web module to provide API for
>> managing OS-level processes. I expect users to pass it a table
>> containing _at_least_ id, process command name, arguments, placeholder
>> for exit code and status string. It is expected that users will use
>> tables containing more problem-specific columns.
>>
>> The problem is that I cant use simple dml operations anymore. As a
>> start, I tried to write dummy insert using [demo/more/orm.ur] as
>> example, but was stopped by difficult [ensql] function. Could you
>> please help me to implement it?  The code is quite short and listed
>> below.
>>
>> Regards,
>> Sergey
>>
>> ---
>>
>> con jobinfo = [
>>     Id = int
>>   , ExitCode = option int
>>   , Cmd = string
>>   , Hint = string
>>   ]
>>
>> functor Make(M : sig
>>
>>   con u
>>
>>   constraint [Id,ExitCode,Cmd,Hint] ~ u
>>
>>   table t : (jobinfo ++ u)
>>
>>   sequence s
>>
>> end) = struct
>>
>>   open CallbackFFI
>>
>>   type row' = record (jobinfo ++ M.u)
>>
>>   (* fun ensql [avail ::_] (r : row') : $(map (sql_exp avail [] []) fs') = *)
>>   (*     @map2 [meta] [fst] [fn ts :: (Type * Type) => sql_exp avail
>> [] [] ts.1] *)
>>   (*      (fn [ts] meta v => @sql_inject meta.Inj v) *)
>>   (*      M.folder M.cols r *)
>>
>>   (* createSync will start the job, but in this example it just does a
>> simple insert.
>>     args is a problem-specific part of the table record.
>>
>>     How to make this dml(insert..) work? *)
>>
>>   fun createSync (ji : record jobinfo, args : record M.u) :
>> transaction (option int) =
>>     i <- nextval M.s;
>>     dml(insert M.t ({Id = sql_inject ji.Id,
>>           ExitCode = sql_inject ji.ExitCode,
>>           Cmd = sql_inject ji.Cmd,
>>           Hint = sql_inject ji.Hint} ++ (ensql args) ));
>>
>>     return (Some i)
>>
>> end
>>
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