Your example doesn't show the functor being applied. The problem would
need to be in the details of that application, since such arguments do
indeed get inferred under many circumstances.
On 02/12/2017 04:56 AM, Sergey Mironov wrote:
Thanks, very interesting. I've managed to fix my original code, it is
attached below.
During the work I discovered a fact that UrWeb automatically infers a
record of [sql_injectable] instances if it is passed as function
argument, but refuses to do so if I try to pass it as Functor
argument. In the latter case, the error is as follows:
Callback1.ur:6:14: (to 12:1) Unmatched signature item
Item: val injs : (fn t :: {Type} => $t) (map sql_injectable u)
Is it a generic limitation or just an undone feature?
Regards,
Sergey
---
con jobinfo = [
Id = int
, ExitCode = option int
, Cmd = string
, Hint = string
]
functor Make(M : sig
con u
val fu : folder u
(* val injs : record (map sql_injectable u) *)
constraint [Id,ExitCode,Cmd,Hint] ~ u
table t : (jobinfo ++ u)
sequence s
end) = struct
type row' = record (jobinfo ++ M.u)
fun createSync (cmd : string)
(injs : record (map sql_injectable M.u))
(fs : record M.u)
: transaction (option int) =
i <- nextval M.s;
dml (insert M.t (
{ Id = sql_inject i,
ExitCode = sql_inject None,
Cmd = sql_inject cmd,
Hint = sql_inject "" } ++
(@Top.map2 [sql_injectable] [ident] [sql_exp [] [] []]
(fn [t] => @sql_inject) M.fu injs fs)
)
);
return (Some i)
end
2017-02-11 16:59 GMT+03:00 Adam Chlipala <[email protected]>:
The key things missing in the original functor argument are a folder for [u]
and a record of [sql_injectable] instances for it, both of which you'll see
used in similar UPO functions mentioned earlier.
BTW, the type of [insert] (in lib/ur/basis.urs) isn't magic and can be
inspected just like any Ur type, and it should be possible to understand
from first principles.
On 02/11/2017 04:19 AM, [email protected] wrote:
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 [email protected]:
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 [email protected]:
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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