bind :: Monad m => (a -> m b) -> m a -> m b

Christopher Allen cma at bitemyapp.com
Tue Dec 9 21:59:02 UTC 2014


I'd love to have a "bind" with that nice symmetry with fmap for both
personal use and for pedagogical purposes. I use precisely that function by
that name to help teach monads already.

On Tue, Dec 9, 2014 at 3:55 PM, Bob Ippolito <bob at redivi.com> wrote:

> +1 from me, I would love to have named versions of these operators.
>
> Does `ap` still have a Monad constraint or has it been changed to match
> the Applicative `<*>` after AMP?
>
> On Tue, Dec 9, 2014 at 1:44 PM, Christopher Done <chrisdone at gmail.com>
> wrote:
>
>> Is this defined anywhere in base, and if not could it be placed in
>> Control.Monad? I often find myself writing:
>>
>> fmap (mu bar)
>>      (foo zot)
>>
>> Then I decide to change the type of x, so instead I want to just
>> write:
>>
>> bind (mu bar)
>>      (foo zot)
>>
>> Which is just like fmap but the function can run in the
>> monad. Similar to traverse:
>>
>> (Traversable t, Applicative f) => (a -> f b) -> t a -> f (t b)
>>
>> As someone who isn’t a fan of operators, I generally am appreciative
>> of alternative regular plain English word versions of functions, which
>> I find easier to type, read and edit. Currently without defining such
>> a handy name, I have to transform the code to this:
>>
>> mu bar =<<foo zot
>>
>> The name for this function is a no-brainer:
>>
>> bind :: Monad m => (a -> m b) -> m a -> m bbind = (=<<)
>>
>> For comparison, the not-very-pleasant <$> and <*> each have word
>> alternatives, fmap and ap. Even <> has mappend.
>>
>> I don’t hold much hope for this, Haskellers love operators as much as
>> Perl programmers so few on this list will see the value in plain old
>> words, but at least I can link to this email in the archives for
>> future reference.
>>
>> Ciao
>>>>
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>>
>
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