Emil Axelsson
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... In particular, the Eq instance for stable names of AST nodes is at https://github.com/AccelerateHS/accelerate/blob/master/Data/Array/Accelerate... You may be able to use our entire scheme. (We have started to write it up as a paper, but the write up isn't in a coherent state yet.) Manuel