[Haskell-cafe] Monad strictness

Wolfgang Jeltsch wolfgang at jeltsch.net
Mon Nov 21 10:22:41 EST 2005

Am Montag, 21. November 2005 16:09 schrieb Roberto Zunino:
> Yitzchak Gale wrote:
> > In the following, why does testA work and testB diverge?
> > Where is the strictness coming from?
> My guess: from strict pattern matching in (>>=).

This is a problem I came across some months ago.  State uses lazy pattern 
matching (implicitely via a let expression) while StateT uses strict pattern 
matching (inside a do statement).  Both should definitely use lazy pattern 
matching, in my opinion.

> [...]

> The following StateT variant uses lazy (irrefutable) pattern match instead.

Good! :-)

> Regards,
> Roberto Zunino.

> [...]

Best wishes,

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