What causes <<loop>>?

Krasimir Angelov kr.angelov at gmail.com
Sat Nov 8 11:47:38 EST 2008


Hi Creighton,

This means that the interpreter have detected that your program run
into infinite loop. There are many possibilities but one of them (the
most often for me) is to have something like:

let x = f x

because of the lazy evaluation this is possible but leads to infinite
loop. It is different from:

x := f x

that you usually do in imperative languages. Sometimes I also forget
to give a new name for x and it results in this kind of infinite loop.


Regards,
  Krasimir

On Sat, Nov 8, 2008 at 5:32 PM, Creighton Hogg <wchogg at gmail.com> wrote:
> Hello,
> So I'm trying to debug an issue that is causing GHC to emit the
> <<loop>> warning.  I was hoping to get more information about what
> exactly that tells me about the kind of problem, other than the
> obvious interpretation that I appear to be getting into some kind of
> infinite loop.  What is GHC detecting when it emits that warning?
>
> Thanks,
> Creighton
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