On 5/7/12 4:02 AM, Simon Peyton-Jones wrote:
|> Can you give a concrete example. It's hard to be certain but what you |> describe sounds like exactly what INLINABLE does.
Your example didn't use any type classes, so GHC won't specialise it.
In order to give a sense of why it matters I only presented the general recurrence rather than the actual Haskell code; in the recurrence the type class is left implicit, but covers (Probability,(*),sum). The actual type of the forward algorithm in the Haskell code is: forward :: ( Enum i , MapLike i map_i , MapLike ts map_ts , SlidingWindow t ts , ExtendedSemiring t sr sr0 ) => map_ts Prob -- ^ Prior probabilities: @Pr( t_{1-k}^0 )@ -> (t -> ts -> Prob) -- ^ Transition probabilities: @Pr( t_j | t_{j-k}^{j-1} )@ -> (w -> t -> Prob) -- ^ Emission probabilities: @Pr( w_j | t_j )@ -> (w -> [t]) -- ^ A tag dictionary for all words -> [w] -- ^ The sentence to be tagged: @w_1^N@ -> (i, map_i (map_ts sr)) -- ^ The final index and table: @(N, alpha)@ The first four arguments are passed in together, but are dynamically defined; and the resulting function will be called on multiple [w]. We will almost certainly satisfy: i ~ Nat -- a newtype of Int map_i ~ NatMap -- a newtype of IntMap; fundep defines i t ~ ID Tag -- a newtype of Int w ~ ID Word -- a newtype of Int and so should definitely specialize on them. That part can be handled by SPECIALIZE since it's well-known. But the important things are the types which are left abstract but which we want to specialize on: ts -- some n-tuple of @t@ for unknown @n@ map_ts -- fundep defines ts sr -- fundep defined by sr0 sr0 -- the semiring-like structure -- Live well, ~wren