Janis Voigtlaender wrote:
Martin Hofmann wrote:
I've already posted this mail on haskell-cafe, but apparently the
subject suggested a too simple question, so I try it here again. I am
picking up a discussion with the same topic from haskell-users on
8th November.
Note that you have been sending to haskell-cafe again. Your recipient
name says haskell-beginners, but the address is haskell-cafe.
Anyway, <<loop>> really means a loop in evalutation order, not some
statebased deadlock (see below).
Thunks with reference on themselves was mentioned as main reason for
<<loop>>.
A safe recursive definition would be
let x = Foo (x+1)
However, if you leave out the constructor,
let x = x + 1
you get a <<loop>> (or a deadlock).
Are there any other reasons?
I am trying to debug monadic code which stores state information in a
record maintaining several Data.Maps, but in vain so far. A state is
modified/changed in several steps by a compound function i.e.
changeA $ changeB $ changeC state
Could this also lead to a deadlock?
I don't think so. At least not in a way that leads to <<loop>>. If you
get <<loop>> then you really have some infinite recursion in your
program. Maybe you can track it down with Debug.Trace.trace.
If so, can I prevent this using CPS?
Oh, that last question was from the original mail, not from my answer.
In any case, I don't think that CPS will help in finding the looping
error in your program.
--
Dr. Janis Voigtlaender
http://wwwtcs.inf.tu-dresden.de/~voigt/
mailto:[EMAIL PROTECTED]
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