How to avoid line splitting in Format.printf?

joelj · December 3, 2018, 12:38pm

Can someone please help me to get rid of the automatic line splitting due to Format.printf for the following piece of code. Using set_margin only seems to work up to a certain limit but doesn’t help for very very long lines.

let () = Map.iteri file_types ~f:(fun ~key:name ~data ->
    Format.printf "%s %s %a@." filename name Pprintast.core_type data
)

The full code is here:

github.com

sepp2k/mli_compatibility/blob/master/Mli_analyser.ml

open Ocaml_common
open Parsetree
open Core

let parse_mli file =
    In_channel.with_file file ~binary:false ~f:(fun in_file ->
        let lexbuf = Lexing.from_channel in_file in
        Parser.interface Lexer.token lexbuf
    )

type ('k, 'v) map = ('k, 'v) Map.Poly.t

let create_map (f: 'a -> ('k * 'v) option) (xs: 'a list): ('k, 'v) map =
    let folder acc x =
        match f x with
        | Some (key, value) ->
            begin match Map.add acc ~key ~data:value with
            | `Ok result -> result
            | `Duplicate -> failwith "Duplicate key in map creation"
            end

This file has been truncated. show original

I’ve tried to use Printf.printf, but the interface is not compatible:

Error: This expression has type Format.formatter -> core_type -> unit
       but an expression was expected of type out_channel -> 'a -> unit
       Type Format.formatter is not compatible with type out_channel

octachron · December 3, 2018, 1:06pm

What is the issue exactly? Did you have an example of unintended line break? Did you remember to set max_indent to margin - 10 after increasing the margin?

joelj · December 3, 2018, 3:25pm

Thanks @octachron! I didn’t know about set_max_indent, that solved the problem.

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How to avoid line splitting in Format.printf?

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