Hi all,
I've a type problem that I cannot solve and, before I keep banging my
head against an unbreakable wall, I'd like to discuss it with the
list.
Consider the following code:
module Main where
class PRead p where {}
class PWrite p where {}
newtype Sealed p a = Sealed a
In ghci I get
let evil = appendLog Foo Bar
interactive:1:11:
Ambiguous type variable `p' in the constraints:
`PRead p'
arising from a use of `appendLog' at interactive:1:11-31
`PWrite p'
arising from a use of `appendLog' at interactive:1:11-31
Probable fix:
On Wed, Feb 9, 2011 at 18:43, Steffen Schuldenzucker
sschuldenzuc...@uni-bonn.de wrote:
...
let good = appendLog Foo Bar :: Sealed Admin String
unseal (undefined :: Admin) good
FooBar
That's true, but putting apart the problem I posed, in my construction
I wouldn't expose unseal directly nor
On Wed, 2011-02-09 at 18:15 +0100, Cristiano Paris wrote:
I've a type problem that I cannot solve and, before I keep banging my
head against an unbreakable wall, I'd like to discuss it with the
list.
If I'm understanding your high-level goals correctly, then you're going
about things the wrong
On 09.02.2011 20:57, Chris Smith wrote:
On Wed, 2011-02-09 at 18:15 +0100, Cristiano Paris wrote:
I've a type problem that I cannot solve and, before I keep banging my
head against an unbreakable wall, I'd like to discuss it with the
list.
If I'm understanding your high-level goals correctly,
On 09.02.2011 20:15, Cristiano Paris wrote:
Now the problem.
I would like to enforce permissions not at the role level, but at the
permissions level. Let's say that I want to leave unseal unchanged,
I'd like to construct a p-value for unseal combining functions
checking for single permissions,
On Wed, Feb 9, 2011 at 19:33, Alexey Khudyakov
alexey.sklad...@gmail.com wrote:
...
If Private is not exported one cannot add instances to PRead.
Nice trick. I would have thought of hiding the classes PRead and
PWrite but I'm not sure if it could break the code.
Thank you!
--
Cristiano
GPG
On Wed, Feb 9, 2011 at 20:14, Alexey Khudyakov
alexey.sklad...@gmail.com wrote:
...
My solution is based on heterogenous lists and require number of
language extensions. I'd recomend to read paper Strongly typed
heterogeneous collections[1] which describe this technique in detail
Curious: I
On Wed, Feb 9, 2011 at 20:14, Alexey Khudyakov
alexey.sklad...@gmail.com wrote:
...
instance PRead (WRead ::: b)
instance PRead b = PRead (a ::: b)
instance PWrite (WWrite ::: b)
instance PWrite b = PWrite (a ::: b)
Brilliant! I was thinking to something like this but
On 09.02.2011 23:16, Cristiano Paris wrote:
On Wed, Feb 9, 2011 at 19:33, Alexey Khudyakov
alexey.sklad...@gmail.com wrote:
...
If Private is not exported one cannot add instances to PRead.
Nice trick. I would have thought of hiding the classes PRead and
PWrite but I'm not sure if it could
On 9 February 2011 19:33, Alexey Khudyakov alexey.sklad...@gmail.com wrote:
On 09.02.2011 20:57, Chris Smith wrote:
On Wed, 2011-02-09 at 18:15 +0100, Cristiano Paris wrote:
I've a type problem that I cannot solve and, before I keep banging my
head against an unbreakable wall, I'd like to
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