[Haskell-cafe] questions on lazy pattern, StateT monad

[Wolfgang Jeltsch]

Am Mittwoch, 23. November 2005 20:42 schrieb Wolfgang Jeltsch:
> Am Mittwoch, 23. November 2005 19:02 schrieb Fan Wu:
> [...]

> > But it is still not clear to me why lazy pattern is used here. Any ideas?
>
> Let's discuss this for State instead of StateT because this makes the
> discussion easier.
>
> [...]

Oops, I've answered a question you didn't ask.  I haven't looked at your 
message carefully enough and thought that you were refering to the 
implementation of (>>=) while in fact you were refering to the implementation 
of mplus.  But I think the reasons behind lazy pattern usage in the mplus 
implementation are similar to those behind lazy pattern usage in the (>>=) 
implementation.

> [...]

Best wishes,
Wolfgang