Hi Conal,
I agree that your initial example is a little puzzling, and I'm glad that the
new ambiguity checker prevents both definitions, not just one.
However, your initial question seems broader than just this example. I have run
into this problem (wanting injective type functions) several tim
Hi Conal,
if you take your example program and write "foo :: Bool", ghci accepts it?
For me it complains, and I would think rightly so, that "couldn't match
expected type Fa with actual type Bool". It actually only works with the
following quite useless "type instance F a = Bool".
By the way, us
On 12 January 2013 16:05, Ian Lynagh wrote:
> On Tue, Jan 08, 2013 at 08:10:18PM +, Duncan Coutts wrote:
>>
>> Either way, lemme know if this is all fine, and I'll make the 0.10.0.2
>> release.
>
> Looks good, thanks! I've updated the GHC 7.6 repo to match the tag.
Ta muchly!
___
Hello,
On Sun, Jan 13, 2013 at 12:05 PM, Conal Elliott wrote:
>
>
> so there is really no way for GHC to figure out what is the intended value
>> for `a`.
>>
>
> Indeed. Though I wonder: does the type-checker really need to find a
> binding for `a` in this case, i.e., given the equation `(forall
Hi Christian,
Given "bar :: Bool", I can't see how one could go from "Bool" to "F a =
> Bool" and determine "a" uniquely.
>
The same question applies to "foo :: Bool", right? Yet no error message
there.
Regards, - Conal
On Sun, Jan 13, 2013 at 11:36 AM, Christian Höner zu Siederdissen <
choe...
Hi Iavor,
Thanks for the remarks.
so there is really no way for GHC to figure out what is the intended value
> for `a`.
>
Indeed. Though I wonder: does the type-checker really need to find a
binding for `a` in this case, i.e., given the equation `(forall a. F a) ==
(forall a'. F a')`?
-- Conal
Hello Conal,
The issue with your example is that it is ambiguous, so GHC can't figure
out how to instantiate the use of `foo`. It might be easier to see why
this is if you write it in this form:
> foo :: (F a ~ b) => b
> foo = ...
Now, we can see that only `b` appears on the RHS of the `=>`, s
Hi,
How would you infer "a" from "F a"? Given "bar :: Bool", I can't see how
one could go from "Bool" to "F a = Bool" and determine "a" uniquely.
My question is not completely retorical, if there is an answer I would
like to know it :-)
Gruss,
Christian
* Conal Elliott [13.01.2013 20:13]:
>
I sometimes run into trouble with lack of injectivity for type families.
I'm trying to understand what's at the heart of these difficulties and
whether I can avoid them. Also, whether some of the obstacles could be
overcome with simple improvements to GHC.
Here's a simple example:
> {-# LANGUAGE
Understood
I've got another RPi supposed to arrive this week - would more computation
power help anyone out there?
Neil
On 13 Jan 2013, at 15:59, rocon...@theorem.ca wrote:
> On Sun, 13 Jan 2013, Neil Davies wrote:
>
>> Sounds like we're close - I must admit I've slightly lost track of the
>
On Sun, 13 Jan 2013, Neil Davies wrote:
Sounds like we're close - I must admit I've slightly lost track of the things
that need to be done.
Can we start collecting the pre-conditionds and steps, when each complete build
takes best part of a day, its difficult to keep the context.
So - taking
Ok, the instruction
ldr r1, [r0, #140] <-> tso = CurrentTSO
seems the assume that REG_Base is r0 (140 is the offset of the tso in
StgRegTable, to which the REG_Base register should point).
But according to MachRegs.h on arm architecture, REG_Base should be r4.
Ineed, when I do
p *(unsigned
Mmh, that does not seem to work.
(gdb) strace
warning: Couldn't determine the static tracepoint marker to probe
Static tracepoint 1 at 0x3f0588
On 01/13/2013 12:56 PM, Conrad Parker wrote:
> On 11 January 2013 19:36, Nathan Hüsken wrote:
>> Hi,
>>
>> I was succesfull in building ghc (pulled from
There is some more success :).
When I do an unregisterised build, it works without segfault.
On 01/13/2013 11:16 AM, Bernhard Urban wrote:
> Hi Nathan,
>
> On Fri, Jan 11, 2013 at 12:36 PM, Nathan Hüsken
> wrote:
>> I was succesfull in building ghc (pulled from git) to compile for
>> arm-linux-a
On 11 January 2013 19:36, Nathan Hüsken wrote:
> Hi,
>
> I was succesfull in building ghc (pulled from git) to compile for
> arm-linux-androideabi!
>
> Now using "inplace/bin/ghc-stage1 -dcore-lint -debug" I compiler this
> Main.hs:
>
> main = putStrLn "Hello, World"
>
> I get an executable, which
Sounds like we're close - I must admit I've slightly lost track of the things
that need to be done.
Can we start collecting the pre-conditionds and steps, when each complete build
takes best part of a day, its difficult to keep the context.
So - taking the ghc 7.4.1 that is part of raspian whee
Hi Nathan,
On Fri, Jan 11, 2013 at 12:36 PM, Nathan Hüsken
wrote:
> I was succesfull in building ghc (pulled from git) to compile for
> arm-linux-androideabi!
Great news!
Can you describe how you managed to build it and which environment you use?
> main = putStrLn "Hello, World"
>
> I get an e
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