Hi,
On 06.06.2007, at 07:00, Phlex wrote:
So here is one more question :
Let's say I want unique System names across the Universe ... that
would mean i need to have a Data.Map in the Universe, with Name
keys and System values. Since all data are values instead of
references, would i end u
apfelmus wrote:
Phlex wrote:
Ketil Malde wrote:
Is the relational model a better fit than the object model for
functional programming ?
Well, not really. I mean, if the problem is indeed to store all known
planets in the universe, then it's indeed a database in nature and you
h
Phlex wrote:
> Ketil Malde wrote:
>> Identity can be emulated by relatively straightforward means: store all
>> planets in a Map indexed by something that is useful as an identifier
>> (i.e. stays constant and is unique), and have a Galaxy keep a list of
>> identifiers.
>>
>
> So basically you
Phlex wrote:
Christopher Lane Hinson wrote:
Where "InsidenessMap a b c" represents a relationship where b's are
inside a's, and b's have a state of c. Then, you need to declare a
separate InsidenessMap for each possible relationship, but this
ensures that you'll never put a galaxy inside
Christopher Lane Hinson wrote:
Where "InsidenessMap a b c" represents a relationship where b's are
inside a's, and b's have a state of c. Then, you need to declare a
separate InsidenessMap for each possible relationship, but this
ensures that you'll never put a galaxy inside a solar system
David Menendez wrote:
| That's a neat idiom. I wonder how far one could usefully generalize it.
|
| For example,
|
| type Ref cx t = forall f. Functor f => (t -> f t) -> cx -> f cx
|
| newtype Id a = Id { unId :: a }
| instance Functor Id where fmap f = Id . f . unId
|
| newtype K
|> > data Ref cx t
|> > = Ref
|> >{
|> > select :: cx -> t
|> >, update :: (t -> t) -> cx -> cx
|> >}
|>
|> A Ref is a bit like a typed and composable incarnation of apfelmus's
|> indices, or a wrapper around Tillmann's change* functions, containing
|> not only a setter but als
Arie Peterson writes:
> There are two things one typically wants to do when working with a
> substructure of some larger data structure: (1) extract the
> substructure; and (2) change the larger structure by acting on the
> substructure. A 'Ref cx t' encodes both of these functions (for a
> substr
Hi
> You could also use 'compositional functional references'. These are
> introduced in the paper "A Functional Programming Technique for Forms in
> Graphical User Interfaces" by Sander Evers, Peter Achten and Jan Kuper.
>
> I've written a template haskell function to derive Refs from a data
(Sorry to break the thread, but mutt somehow managed to eat the message
I'm replying to...)
Arie Peterson:
> You could also use 'compositional functional references'. These are
> introduced in the paper "A Functional Programming Technique for Forms in
> Graphical User Interfaces" by Sander Evers,
You could also use 'compositional functional references'. These are
introduced in the paper "A Functional Programming Technique for Forms in
Graphical User Interfaces" by Sander Evers, Peter Achten and Jan Kuper.
=== Introduction ===
There are two things one typically wants to do when working wit
Let's say i have a deep nested data structure.
Universe containing galaxies, containing solar systems, containing
planets, containing countries, containing inhabitants, containing
...whatever.
Oh. I had /exactly/ this problem. If you use separate types (i.e. a
newtyped integer, acting kindo
apfelmus wrote:
> {-# OPTIONS_GHC -fglasgow-exts -#}
> import Prelude hiding (lookup)
>
> class Map map key a | map key -> a where
> lookup :: key -> map -> Maybe a
> adjust :: (a -> a) -> key -> map -> map
>
> instance (Map m k m', Map m' k' a) => Map m (k,k') a w
apfelmus wrote:
Phlex wrote:
Donald Bruce Stewart wrote:
Yes and no. The point is that if you can't automate it, you have to code
it by hand anyway which constitutes most of the hairiness. But I know
what you mean and there's a nice way to do that with multi-parameter
type classes.
Let
apfelmus:
> Phlex wrote:
> > Donald Bruce Stewart wrote:
> >>
> >> Imagine updating a node in a tree by just detaching and reattaching a
> >> pointer.
> >>
> >> [1] [1]
> >> / \ / \
> >> [2] [3] update node 5 [2] [3]
> >> / \
Phlex wrote:
> Donald Bruce Stewart wrote:
>>
>> Imagine updating a node in a tree by just detaching and reattaching a
>> pointer.
>>
>> [1] [1]
>> / \ / \
>> [2] [3] update node 5 [2] [3]
>> / \ with value 7 / \
>>
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