[Haskell-cafe] Function hanging in infinite input

Jerzy Karczmarczuk jerzy.karczmarczuk at unicaen.fr
Sun Apr 26 17:05:01 UTC 2015

Martin reacts to my non-answer:
> Am 04/26/2015 um 05:28 PM schrieb Jerzy Karczmarczuk:
> ...
> and GHCi says:
> *Main> ex10
> *** Exception: Prelude.head: empty list
> This is because I have commented out two corner cases in tBind, to make sure it's not them. Remove the comments and
> it'll work
Martin I sent you a private follow-up. I repeat it here.

I uncommented those lines.
Your program goes until the end of the list, and returns the /*last*/ 
element (modified).  The form

*tBind tpr f
  (tTail tpr `tBind` f) *

loops until ...

Now, I know about laziness... It seems that it doesn't help. Most 
probably your hd is simply empty, and the tail gets stuck in an idle loop.

Jerzy Karczmarczuk

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