Re: [Caml-list] format strings

[Jiten Pathy <jpathy@fssrv.net>]

Thanks, that helps. I can't think of any complicated manipulation i
would need, for now.

On Tue, Feb 10, 2015 at 12:25 AM, David Allsopp <dra-news@metastack.com> wrote:
> Jiten Pathy wrote:
>> Ok, If i am not supposed to use make_printf, then what is the recommended
>> way of writing the following?
>>
>> This adds a new line to given format string. In particular how do i
>> manipulate the format strings passed to me?
>
> There wasn't a vast amount of type-safe manipulation possible with format strings in the old implementation, though given the newer representation, perhaps something may come in the future.
>
>> open CamlinternalFormat;;
>> let f (Format (fmt, _)) =
>>   make_printf (fun o acc -> output_acc o (Acc_char_literal (acc, '\n'));
>> ignore o) stdout End_of_acc fmt ;; val f : ('a, out_channel, unit, unit,
>> unit, unit) format6 -> 'a = <fun>
>>
>> utop # f "%s %d" "# " 3;;
>> #  3
>> - : unit = ()
>
> However, for this "simple" manipulation there are two ways which don't touch the internals:
>
> let f fmt = Printf.ksprintf (Printf.printf "%s\n") fmt
>
> [that's my preference - to me it's clearer that you're wrapping the formatted output. I'd often do this to add %! as well - i.e. "%s\n%!"]
>
> let f fmt = Printf.printf (fmt ^^ "\n")
>
> [See http://caml.inria.fr/pub/docs/manual-ocaml-4.02/libref/Pervasives.html#6_Operationsonformatstrings]
>
>
> David