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Today's Topics:
1. Re: Monad for Pair (Mike Houghton)
2. Re: Monad for Pair (Mike Houghton)
3. Functional Programming for the Object Oriented (?ystein Kolsrud)
4. Applicative Laws for the ((->) r) type (Umair Saeed)
5. Learning Haskell: Higher-order Functions (Manuel M T Chakravarty)
6. Re: Monad for Pair (Kim-Ee Yeoh)
----------------------------------------------------------------------
Message: 1
Date: Wed, 18 Nov 2015 18:33:35 +0000
From: Mike Houghton <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Monad for Pair
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
'Much better if you let us know the source of this problem. Is this an exercise
from some book / online course??
The source is just me exploring.
I first looked at
data C a = C a deriving (Show)
and made Monad, Applicative, Monoid and Functors for it.
So then tried
Pair a = P (a, a)
and stuck on Monad.
Thanks
Mike
> On 18 Nov 2015, at 07:23, Kim-Ee Yeoh <[email protected]
> <mailto:[email protected]>> wrote:
>
>
> On Wed, Nov 18, 2015 at 4:41 AM, Mike Houghton <[email protected]
> <mailto:[email protected]>> wrote:
>
> And really return x = P (x, x) doesn?t seem correct anyway.
>
> But if you look at the type, which is essentially "a -> (a,a)" there's only
> one way to write it, for the same reason that there's only one "a -> a"
> function.
>
> Would someone please write the Monad with an explanation?
>
> Much better if you let us know the source of this problem. Is this an
> exercise from some book / online course?
>
> -- Kim-Ee
> _______________________________________________
> Beginners mailing list
> [email protected] <mailto:[email protected]>
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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Message: 2
Date: Wed, 18 Nov 2015 18:33:59 +0000
From: Mike Houghton <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Monad for Pair
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
'Much better if you let us know the source of this problem. Is this an exercise
from some book / online course??
The source is just me exploring.
I first looked at
data C a = C a deriving (Show)
and made Monad, Applicative, Monoid and Functors for it.
So then tried
Pair a = P (a, a)
and stuck on Monad.
Thanks
Mike
> On 18 Nov 2015, at 07:23, Kim-Ee Yeoh <[email protected]
> <mailto:[email protected]>> wrote:
>
>
> On Wed, Nov 18, 2015 at 4:41 AM, Mike Houghton <[email protected]
> <mailto:[email protected]>> wrote:
>
> And really return x = P (x, x) doesn?t seem correct anyway.
>
> But if you look at the type, which is essentially "a -> (a,a)" there's only
> one way to write it, for the same reason that there's only one "a -> a"
> function.
>
> Would someone please write the Monad with an explanation?
>
> Much better if you let us know the source of this problem. Is this an
> exercise from some book / online course?
>
> -- Kim-Ee
> _______________________________________________
> Beginners mailing list
> [email protected] <mailto:[email protected]>
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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Message: 3
Date: Wed, 18 Nov 2015 20:35:42 +0100
From: ?ystein Kolsrud <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Functional Programming for the Object
Oriented
Message-ID:
<CAH_oh=wOZaqkSJvZ4ap3chsWHfm3aAsft4=zgdkk4fsddla...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
I gave a presentation on functional programming a couple of weeks ago
that I thought might be of interest to this community as well:
https://www.youtube.com/watch?v=I2tMmsZC1ZU
It's target audience is programmers familiar with object oriented
programming, and it presents how concepts from the functional paradigm
are relevant also in most modern OO languages.
For more information about the presentation, please refer to the following site:
http://www.foocafe.org/previous_event/functional-programming-for-the-object-oriented
--
Mvh ?ystein Kolsrud
------------------------------
Message: 4
Date: Wed, 18 Nov 2015 17:03:50 -0800
From: Umair Saeed <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Applicative Laws for the ((->) r) type
Message-ID:
<cad2rvxao7jsrdiofdsm9s3rhxps9vc_0+qrl312hwzkammt...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi all,
I'm trying to check that the Applicative laws hold for the function type ((->)
r), and here's what I have so far:
-- Identiy
pure (id) <*> v = v
pure (id) <*> v
const id <*> v
(\x -> const id x (g x))
(\x -> id (g x))
(\x -> g x)
g x
v
-- Homomorphism
pure f <*> pure x = pure (f x)
pure f <*> pure x
const f <*> const x
(\y -> const f y (const x y))
(\y -> f (x))
(\_ -> f x)
pure (f x)
Did I perform the steps for the first two laws correctly?
I'm struggling with the interchange & composition laws. For interchange, so
far I have the following:
-- Interchange
u <*> pure y = pure ($y) <*> u
u <*> pure y
u <*> const y
(\x -> g x (const y x))
(\x -> g x y)
-- I'm not sure how to proceed beyond this point.
I would appreciate any help for the steps to verify the Interchange &
Composition applicative laws for the ((->) r) type.
Thank you,
~Umair
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Message: 5
Date: Thu, 19 Nov 2015 14:26:31 +1100
From: Manuel M T Chakravarty <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Learning Haskell: Higher-order Functions
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
We have got a new tutorial chapter on ?Higher-order Functions & Combinators?:
http://blog.haskellformac.com/blog/higher-order-functions-combinators
Hope you enjoy it!
Manuel
------------------------------
Message: 6
Date: Thu, 19 Nov 2015 13:34:48 +0700
From: Kim-Ee Yeoh <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Monad for Pair
Message-ID:
<CAPY+ZdS-RxU9o5bpB70Jt=ot8ul72vj5d9+rrvj9nz4oz5u...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
On Thu, Nov 19, 2015 at 1:33 AM, Mike Houghton <[email protected]>
wrote:
The source is just me exploring.
>
Nice.
> I first looked at
>
> data C a = C a deriving (Show)
>
> and made Monad, Applicative, Monoid and Functors for it.
>
Even though the null-effect instances for the identity functor are trivial,
there's value in writing them out, especially for the motivated.
But how do you take an arbitrary type and turn it into a monoid?
-- Kim-Ee
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