I really liked this explanation -- very clear, with good analogies.
Thanks!
Martin
My music: http://www.youtube.com/profile?user=thetonegrove
Claus Reinke wrote:
quantified types (forall/exist):
an easy way to memorize this is to think of 'forall' as a big 'and'
and of 'exists' as a big
On Tue, 2007-05-29 at 21:28 +0100, Andrew Coppin wrote:
phantom types:
the types of ghost values (in other words, we are only interested in
the type, not in any value of that type).
Mmm... Still not seeing a great amount of use for this one.
The point is to 'tag' something with a type
quantified types (forall/exist):
an easy way to memorize this is to think of 'forall' as a big 'and'
and of 'exists' as a big 'or'.
e :: forall a. a -- e has type 'Int' and type 'Bool' and type ..
e :: exists a. a -- e has type 'Int' or type 'Bool' or type ..
That doesn't entirely
On 5/29/07, Andrew Coppin [EMAIL PROTECTED] wrote:
Claus Reinke wrote:
phantom types:
the types of ghost values (in other words, we are only interested in
the type, not in any value of that type).
Mmm... Still not seeing a great amount of use for this one.
Okay,
Hi Andrew!
I share your concerns about the simplicity of the language. Once
extensions exists, they are used widely, and readers of programs must
understand them, also if the extensions are used without need. I
understand the motivations for many type extensions, but library writers
tend to use
| I wish the compilers would allow more fine grained switches on languages
| extensions. -fglasgow-exts switches them all on, but in most cases I'm
| interested only in one. Then typing errors or design flaws (like 'type
| Synonym = Type', instead of wanted 'type Synonym a = Type a'; extended
|
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Simon Peyton-Jones wrote:
| I wish the compilers would allow more fine grained switches on languages
| extensions. -fglasgow-exts switches them all on, but in most cases I'm
| interested only in one. Then typing errors or design flaws (like 'type
On Tue, May 29, 2007 at 12:41:19PM -0400, Isaac Dupree wrote:
Simon Peyton-Jones wrote:
| I wish the compilers would allow more fine grained switches on languages
| extensions. -fglasgow-exts switches them all on, but in most cases I'm
| interested only in one. Then typing errors or design
Claus Reinke wrote:
I'm thinking more about things like phantom types, rank-N
polymorphism, functional dependencies, GADTs, etc etc etc that nobody
actually understands.
this seems to be overly polymorphic in generalising over all types of
Haskell programmers, rather than admitting the
I'm thinking more about things like phantom types, rank-N polymorphism,
functional dependencies, GADTs, etc etc etc that nobody actually
understands.
this seems to be overly polymorphic in generalising over all types of
Haskell programmers, rather than admitting the existence of some types
apfelmus wrote:
Andrew Coppin wrote:
OOC, can anybody tell me what ∀ actually means anyway?
http://en.wikipedia.org/wiki/Universal_quantification
http://en.wikipedia.org/wiki/System_F
So... ∀x . P means that P holds for *all* x, and ∃ x . P means that x
holds for *some* x?
On 27/05/07, Andrew Coppin [EMAIL PROTECTED] wrote:
So... ∀x . P means that P holds for *all* x, and ∃ x . P means that x
holds for *some* x? (More precisely, at least 1 possible choice of x.)
Exactly. There's also a lesser-used there exists a unique, typically
written ∃!x. P, which means that
On May 27, 2007, at 9:19 , Andrew Coppin wrote:
So... ∀x . P means that P holds for *all* x, and ∃ x . P means
that x holds for *some* x? (More precisely, at least 1 possible
choice of x.)
Exactly.
Seriously. Haskell seems to attract weird and wonderful type system
extensions like a 4
Erm... oh...kay... That kind of makes *slightly* more sense now...
I wrote most of the second article, I'd appreciate any feedback you
have on it.
If I'm understanding this correctly, existentially quantified types
(couldn't you find a name that's any harder to
remember/pronounce/spell?)
On Sun, 27 May 2007, Andrew Coppin wrote:
Seriously. Haskell seems to attract weird and wonderful type system extensions
like a 4 Tesla magnet attracts iron nails... And most of these extensions seem
to serve no useful purpose, as far as I can determine. And yet, all nontrivial
Haskell
Brandon S. Allbery KF8NH wrote:
Seriously. Haskell seems to attract weird and wonderful type system
extensions like a 4 Tesla magnet attracts iron nails... And most of
these extensions seem to serve no useful purpose, as far as I can
determine. And yet, all nontrivial Haskell programs
On Sun, 27 May 2007, Andrew Coppin wrote:
I'm thinking more about things like phantom types, rank-N polymorphism,
functional dependencies, GADTs, etc etc etc that nobody actually understands.
I think you'll find a fair number of people do in fact understand them!
This worries me greatly.
Hello Andrew,
Sunday, May 27, 2007, 5:19:51 PM, you wrote:
Seriously. Haskell seems to attract weird and wonderful type system
extensions like a 4 Tesla magnet attracts iron nails... And most of
these extensions seem to serve no useful purpose, as far as I can
determine.
existentials is
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