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To: caml-list@yquem.inria.fr
Subject: Format: Fortran (&c.) style continuation lines?
Reply-To: ohl@physik.uni-wuerzburg.de
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Date: Thu, 8 Apr 2010 12:58:28 +0200 (CEST)
From: ohl@physik.uni-wuerzburg.de (Thorsten Ohl (TP2))
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X-Spam: no; 0.00; ohl:01 thorsten:01 ohl:01 foo:01 printf:01 foo:01 printf:01 -thorsten:01 thorsten:01 wuerzburg:01 lexical:01 functions:01 functions:01 bin:01 newline:02 

Hi,

for ages, I've been using the following (somewhat hackish) approach to
pretty printing source code that requires special lexical markers to
allow statements that continue over more than one line.  (e.g. in
Fortran

  foo = 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 &
     + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 &
     + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 &
     + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 &
     + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 &
     + 1 + 1 + 1 + 1 + 1 + 1 + 1

and in /bin/sh we have the same with "\\" instead of "&"):

  open Format;;

  let continuing = ref true;;

  let wrap_newline () =
    let out, flush, newline, space = get_all_formatter_output_functions
    () in
    let newline' () =
      if !continuing then
        out " &" 0 2;
      newline () in
    set_all_formatter_output_functions out flush newline' space;;

  let nl () =
    continuing := false;
    print_newline ();
    continuing := true;;

  let _ =
    wrap_newline ();;

  (* Nonsensical example: *)
  for statement = 1 to 3 do
    printf "  @[<2>foo = 1";
    for i = 1 to 100 do
      printf "@, + 1"
    done;
    nl ()
  done;;

The requirement to end each statement with "nl ()" is tedious in real
world applications and the use of the global variable "continuing"
violates my sense of aesthetics...

Is there a more idiomatic approach that I'm missing?

Thanks,
-Thorsten
-- 
Thorsten Ohl, Wuerzburg Univ., Physics -- http://physik.uni-wuerzburg.de/ohl