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,
Benoīt 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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