2012-08-26 08:03, Manuel M T Chakravarty skrev:
Emil Axelsson <e...@chalmers.se>:
2012-08-24 11:08, Simon Marlow skrev:
On 24/08/2012 07:39, Emil Axelsson wrote:
Hi!
Are there any dangers in comparing two StableNames of different type?
stEq :: StableName a -> StableName b -> Bool
stEq a b = a == (unsafeCoerce b)
I could guard the coercion by first comparing the type representations,
but that would give me a `Typeable` constraint that would spread
throughout the code.
It should be safe even if the types are
different, but I presume you expect the types to be the same, since
otherwise the comparison would be guaranteed to return False, right?
No, I want to do observable sharing of heterogeneously typed expressions which
means I will be comparing expressions of different type.
You may like to have a look at how we have done this in the Accelerate EDSL:
https://github.com/AccelerateHS/accelerate/blob/master/Data/Array/Accelerate/Smart.hs
In particular, the Eq instance for stable names of AST nodes is at
https://github.com/AccelerateHS/accelerate/blob/master/Data/Array/Accelerate/Smart.hs#L763
Hm, doesn't this impose a `Typeable` constraint on all AST nodes (which
is what I'm trying to avoid)?
/ Emil
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