Re: [Caml-list] Format questions

[Matej Kosik <5764c029b688c1c0d24a2e97cd764f@gmail.com>]

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.