# Disabling Format wrapping

**URL:** <https://discuss.ocaml.org/t/disabling-format-wrapping/15180>\
**Category:** Learning\
**Created:** [August 22, 2024, 9:46am UTC](https://discuss.ocaml.org/t/disabling-format-wrapping/15180 "2024-08-22T09:46:08Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Leonidas](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/leonidas/32/4039_2.png) [@Leonidas](https://discuss.ocaml.org/u/Leonidas)\
**Post date:** [August 22, 2024, 9:46am UTC](https://discuss.ocaml.org/t/disabling-format-wrapping/15180/1 "2024-08-22T09:46:08Z")

</div>

Hi fellow Caml-wranglers,

I ran across an unexpected behavior while trying do disable wrapping in `Format`. From what I understand the wrapping in `Format` is dependent on the value of `margin`, thus setting it to a large value (like `Format.pp_infinity`) should disable wrapping.

```ocaml
Format.printf "@[<hov>This is a long text that I want to print aaa bbb@ ccc ddd eee @[<hov>fff gg hh iii jjjj@] kkk lll mmm n o@]";;

```

This will wrap at the space hint. So

```ocaml
Format.set_margin 100000;
Format.printf "@[<hov>This is a long text that I want to print aaa bbb@ ccc ddd eee @[<hov>fff gg hh iii jjjj@] kkk lll mmm n o@]";;

```

this makes it all print out in one line. So far so good. But if I try the same with `Format.asprintf`:

```ocaml
Format.set_margin 100000;
Format.asprintf "@[<hov 2>This is a long text that I want to print aaa bbb@ ccc ddd eee @[<hov>fff gg hh iii jjjj@] kkk lll mmm n o@]";;

```

I get a `\n` in my string, thus it is wrapping, despite the `margin` setting.

On the other hand, if I specifically set the margin in the format string, it works properly:

```ocaml
Format.asprintf "%a@[<hov 2>This is a long text that I want to print aaa bbb@ ccc ddd eee @[<hov>fff gg hh iii jjjj@] kkk lll mmm n o@]" Format.pp_set_margin Int.max_int;;

```

What is going on and how can I disable the wrapping manually without having to annotate every format string?

---

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**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\
**Post date:** [August 22, 2024, 9:53am UTC](https://discuss.ocaml.org/t/disabling-format-wrapping/15180/2 "2024-08-22T09:53:48Z")

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> [@Leonidas](#):
>
> What is going on and how can I disable the wrapping manually without having to annotate every format string?

`Format.asprintf` creates its own formatter each time it is called; and I do not think it is possible to modify the options of that formatter (like the `margin`).

But you can easily cook your own formatter using `Format.formatter_of_buffer`, change the margin with `Format.pp_set_margin`, and print to it using `Format.fprintf`.

Cheers,  
Nicolas

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**Author:** ![jjb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/jjb/32/2713_2.png) [@jjb](https://discuss.ocaml.org/u/jjb)\
**Post date:** [August 22, 2024, 12:44pm UTC](https://discuss.ocaml.org/t/disabling-format-wrapping/15180/3 "2024-08-22T12:44:41Z")

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It is possible to get ahold of the formatter `asprintf` uses and set the margin:

```auto
  Format.asprintf "%tblah" (fun ppf ->
      Format.pp_set_margin ppf Format.pp_infinity ;
      Format.pp_set_max_indent ppf (Format.pp_infinity - 1) )

```

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<div class="post-metadata">

**Author:** ![Leonidas](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/leonidas/32/4039_2.png) [@Leonidas](https://discuss.ocaml.org/u/Leonidas)\
**Post date:** [August 23, 2024, 12:29pm UTC](https://discuss.ocaml.org/t/disabling-format-wrapping/15180/4 "2024-08-23T12:29:08Z")

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Thanks you two, @nojb for the explanation and @jjb for the workaround. Ended up landing something that uses `pp_set_margin` in a place that gets called by all places that I cared about.