Hi Matej,

I do not think that is the reason, as both calls do the same thing, see

  https://github.com/ocaml/ocaml/blob/trunk/stdlib/format.ml#L1153

Cheers,
Nicolas


On Sun, Apr 9, 2017 at 9:44 AM, Matej Kosik <
5764c029b688c1c0d24a2e97cd764f@gmail.com> wrote:

> Hi Josh,
>
> On 04/09/2017 12:24 AM, Josh Berdine wrote:
> > On Sat, Apr 08 2017, Matej Kosik wrote:
> >
> >> Hi everybody,
> >>
> >> I am trying to understand the concepts in the Format module.
> >>
> >> While reading this:
> >>
> >>   https://ocaml.org/learn/tutorials/format.html
> >>
> >> One of the mini experiments I did was:
> >>
> >>   set_margin 11;
> >>   open_hvbox 0;
> >>   print_string "---";
> >>   print_space ();
> >>   print_string "---";
> >>   print_space ();
> >>   print_string "---";
> >>   print_newline ();
> >>   print_newline ();
> >>
> >> I've got the expected output, which is:
> >>
> >>   ---
> >>   ---
> >>   ---
> >>
> >> No surprises.
> >>
> >> However, when I tried to write express the same intentions via
> Format.fprintf function:
> >>
> >>   Format.set_margin 11;
> >>   Format.fprintf std_formatter "@[<hv 0>---@ ---@ ---@.@.";
> >>
> >> I get:
> >>
> >>   --- --- ---
> >>
> >> I'd like to ask for some clues as to why the output of the above
> Format.fprintf is different from the more verbose version above.
> >
> > Are you, by chance, evaluating this in utop (which seems to mess with
> std_formatter)?   I see your expected behavior using the standard
> toplevel.  (After adding Format. to std_formatter)
>
> I was using standard Ocaml toplevel
> (in a context where I opened Format module).
>
> I looked at it today and I have realized that instead of this:
>
>   set_margin 11;
>
> if I want to use "Format.fprintf std_formatter" I should do
>
>   pp_set_margin std_formatter 11;
>
> as if
>
>   set_margin <> pp_set_margin std_formatter
>
> That I did not know.
>
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