Re: Proposal: Add concatMapM function (#2042)

3 Feb 2008


      Aaron Denney wrote:
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On 2008-02-01, Roman Leshchinskiy  wrote:
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Aaron Denney wrote:
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Bulat Ziganshin wrote:
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the right way to deal with "modifiers" is to attach them to the Handle
itself like this:
f <- openFile "name" >>= withLocking >>= withEncoding utf8
IMO, global state is never "the right way" if it can be avoided. It will 
always lead to problems. Especially in a functional language like Haskell.
This isn't global state, but local to the handle, and only affects where
On 2008-02-01, Roman Leshchinskiy  wrote:
the handle is passed in.  It's just extending an opaque data type.
If I can destructively change the encoding assocated with a Handle, then 
it's global state.
Right.  But the example given doesn't necessarily have that.
x <- [5, 6] >>= (return .) (+ 1)
No modification is going on, but return of new values.
True, but that is a very obfuscated way of doing this. If the handle is 
not modified destructively, then there is no need for withLocking etc. 
to be monadic.

Roman