Maybe Monoid spilt milk

Clifford Beshers clifford.beshers at
Thu Nov 29 14:08:21 EST 2007

Jeremy Shaw and I had a bunch of conversations about this kind of thing,
almost always ending with Jeremy citing this story.  I found it at:

<famous-anecdote>Stuart Feldman, the Bell Labs guy who invented "make", woke
> up one morning a few weeks after he'd released it, and realized that the
> syntax basically sucked - all those tabs and colons and weird continuation
> rules. He started working on something better and was shot down because
> someone said "Stuart, there are *dozens* of people using this, it's too late
> to change it."</famous-anecdote>

Please publish your alternative implementation in a blog or in a package on
Haskell.  Think of all the children that will be spared in the future.


On Nov 29, 2007 10:29 AM, Conor McBride <ctm at> wrote:

> Hi folks
> I realise I should have been paying more attention last March,
> and as such have no reason to expect any sympathy, let alone
> action.
> I would, however, like to comment on the fact that the
> Data.Monoid instance for (Maybe x) prioritises monoidal
> structure from x over monoidal structure from Maybe. This
> makes it hard to use generic monoidal operations to support
> choice in the Maybe monad.
> I don't know if this breaks anybody else's code, but it
> certainly breaks mine. I guess I'll just have to stop using
> Data.Monoid and roll my own. That's not a serious hardship,
> I suppose.
> I have only myself to blame, and I'm not proposing that the
> Maybe behaviour is changed. I suppose people are busy enjoying
> the instance as it now stands, and that it would be damaging
> to change.
> What a pity
> Conor
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