Hi,

The set_margin function configure the std_formatter, ie the formatter of
the standard output (the one used by printf). To change the margin when
printing in a buffer, you can run something like this :

# open Format;;
# let buf = Buffer.create 16;;
val buf : Buffer.t = <abstr>
# let formatter = formatter_of_buffer buf;;
val formatter : Format.formatter = <abstr>
# pp_set_margin formatter 9;;
- : unit = ()
# fprintf formatter "@[<hov0>111,@,222,@,333,@,444,@,555,@,666@]@.";;
- : unit = ()
# Buffer.contents buf;;
- : string = "111,222,\n333,444,\n555,666\n"

Best regards,
Benoît Vaugon.



2014-03-06 17:34 GMT+01:00 Matthieu Dubuget <matthieu.dubuget@gmail.com>:

> Is the following behaviour expected, or a misunderstanding of mine?
>
> In short, I'd like to use the Format module to prepare an
> output inside a Buffer.t. But a basic <hov> box does not
> break lines as I would expect, while printf does.
>
> OCaml version 4.01.0
>
> # open Format;;
> # printf "@[<hov0>111,@,222,@,333,@,444,@,555,@,666@]@.";;
> 111,222,333,444,555,666
> - : unit = ()
> # set_margin 9;;
> - : unit
> = ()
> # printf "@[<hov0>111,@,222,@,333,@,444,@,555,@,666@]@.";;
> 111,222,
> 333,444,
> 555,666
> - : unit
> = ()
> # sprintf "@[<hov0>111,@,222,@,333,@,444,@,555,@,666@]@.";;
> - : string
> =
> "111,222,333,444,555,666\n"
>
> Why doesn't sprintf exhibit the same behaviour as printf?
> Trying with fprintf...
>
> # fprintf str_formatter "@[<hov0>111,@,222,@,333,@,444,@,555,@,666@]@.";;
> - : unit
> = ()
> # flush_str_formatter ();;
> - : string
> =
> "111,222,333,444,555,666\n"
>
> --
> Matthieu Dubuget
>
>
> --
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