Re: Tail calls (Was Re: [Caml-list] Does Caml have slow arithmetics ?)

[Richard Jones <rich@annexia.org>]

This discussion of tail calls is very interesting.

I understand what Xavier is saying about ocamlopt not optimizing badly
written code.  Despite this, I have to say that ocamlopt does a
fantastic job!

However, I think there is one bit of badly written code where it would
be nice if the compiler could do a little bit more optimization,
namely functions such as:

let rec input_all_lines chan =
  try
    let line = input_line chan in
    line :: input_all_lines chan
  with
      End_of_file -> []

The reason is that (as discussed previously, so please don't repost)
the tail-recursive version of this sort of code is quite a bit more
complicated, and therefore quite a bit harder to remember.

Note that the specific input_all_lines function should be in a library
- it is in ExtLib, I think.  However I use that code /pattern/ quite
frequently, particularly when iterating over something which can throw
a Not_found or End_of_file exception and building a structure from the
result.  So I need to remember the optimized version of the pattern,
which my poor brain can't do.

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
MOD_CAML lets you run type-safe Objective CAML programs inside the Apache
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