On Mon, 19 Jan 2004, Richard Jones wrote:
> * Syntactic support for processing lines in a file, ie:
> 
> 	while (<>) { ... }
> 
>   which is an astonishing piece of brevity.  It reads all the command line
>   arguments, opens the files specified and hands them line-at-a-time to
>   the code inside the while loop.  I think ExtLib has some functionality
>   to do a small part of this.  It should be included in the standard
>   distribution.

Opening all files presented on the command line and passing them to some
user-specified function can be easily done using higher-order functions,
e.g.:

  let all_lines f =
    for i = 1 to Array.length Sys.argv - 1 do
      let ic = open_in Sys.argv.(i) in
      try while true do f (input_line ic) done
      with End_of_file -> close_in ic
    done

Putting functions like "all_lines" into a utility module, you can use
"#load" to apply it from scripts:

  #load "util.cmo"
  open Util
  let _ = all_lines print_endline

I don't see a need for syntactic support. Adding two very short lines
to the top of your script (one-time effort) is hardly distracting.

> * Syntactic support for regular expression matching / substring extraction.
> 
>   (As discussed before.)

People often abuse this Perl-feature, because they don't know how to
write lexers/parsers using generators, which would sometimes be the
better choice.

> * No (visible) compilation required.
> 
>   #!/usr/bin/perl
> 
>   Very useful.  There was some discussion before about writing scripts
>   starting with:
> 
>   #!/usr/bin/ocaml

You don't need compilation with OCaml if you want to do scripting!

All you need to do is create a toplevel using the "-custom"-flag, e.g.:

  ocamlmktop -custom -o mytop

This is required under Unix, because only binary executables can be used
for interpretation due to security concerns.

Then write a script like this (assuming that mytop is in the same
directory - you can place it elsewhere, of course):

  #!mytop

  #load "unix.cma"
  open Unix

  let _ = Printf.printf "%f\n" (Unix.gettimeofday ())

As you can see, even loading modules (here: Unix) that use shared
libraries works like a charm.

Btw., what's the reason why "ocaml" is not installed using "-custom"
by default? The size of the executables is almost the same, and people
could more easily use OCaml for scripting then.

> * Certain idiomatic forms, such as:
> 
> 	statement if condition;
>   and:	statement unless condition;
> 
>   which reduce code size.

Too much redundancy with control constructs is not a good idea, IMHO.
The gain is just too small.

> * Absolutely huge library.
> 
>   I'm trying to do my bit here by writing libraries, and specifically
>   with perl4caml which allows you to use Perl libraries with OCaml.  A
>   central CPAN-like resource would still be very useful.

I agree that there could be more and better libraries around. But that's
true for any language whose programmers want to be lazy. ;-)

Regards,
Markus

-- 
Markus Mottl          http://www.oefai.at/~markus          markus@oefai.at

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