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Subject: Re: [Caml-list] Dbi: proposal #1
From: Damien Pous <Damien.Pous@ens-lyon.fr>
To: caml-list@inria.fr
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Le jeu 12/06/2003 =C3=A0 21:07, Christophe TROESTLER a =C3=A9crit :
> Well, you cannot quite do that since (as you noted) you must know the
> type of the argument.  Actually you have two choices: either you
> convert your arguments manually to the [string option array] format or
> you specify the type.  Here you can equivalently write either
> let res =3D dbh#raw_exec query [| Some(string_of_int 10000) |] in
> or
> let res =3D dbh#exec query (t#int) 10000 in

with the CVS Printf.kprintf, you can do something like
<<
type res =3D int

class ['a] query (q: ('a, unit, string, res) format) =3D=20
object(self)
  method execute =3D Printf.kprintf self#execute_string q
  method execute_string =3D String.length (* or sthg more interesting *)
end

class dbh =3D=20
object
  method prepare : 'a. ('a, unit, string, res) format -> 'a query =3D=20
    new query
end

let dbh =3D new dbh
let q1 =3D dbh#prepare "toto %d"
let q2 =3D dbh#prepare "titi %s %f"
let a1 =3D q1#execute 1000=20
let a2 =3D q2#execute "arf" 3.3
>>

if you are not using the cvs version, you can still use exceptions, but
this becomes quite ugly

hope this helps,
damien


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