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From: Roland Zumkeller <roland.zumkeller@gmail.com>
Date: Wed, 1 Jul 2009 11:43:19 +0700
Message-ID: <d02dcb040906302143t2c96fd80t7a1da27cab99844c@mail.gmail.com>
Subject: List.combine stack overflow
To: caml-list@yquem.inria.fr
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X-Spam: no; 0.00; recursion:01 stdlib:01 stack:01 stack:01 rec:01 rec:01 match:02 arg:03 library:03 let:03 let:03 overflow:03 overflow:03 compiled:04 fails:05 

Hi,

List.combine fails in this example:

# let rec ulist = function 0 -> [] | n -> () :: ulist (n-1);;
...
# let x = ulist 30000;;
...
# List.combine x x;;
Stack overflow during evaluation (looping recursion?).

However, with a *copy* of 'combine' from stdlib/list.ml it suddenly works:

# let rec combine l1 l2 =
  match (l1, l2) with
    ([], []) -> []
  | (a1::l1, a2::l2) -> (a1, a2) :: combine l1 l2
  | (_, _) -> invalid_arg "List.combine";;
...
# combine x x;;
[((), ()); ((), ()); ((), ()); ((), ()); ((), ()); ((), ()); ...]

Why does 'combine' in the standard library behave differently from its
own copy? Is it compiled with different options?

Best,

Roland