added model to updatestate!!

Author: torfjelde

docs/src/api.md

@@ -161,7 +161,7 @@ function AbstractMCMC.step(rng, model::AbstractMCMC.AbstractModel, sampler::Mixt
     # the state and transition from the previous iteration.
     i_prev = state.index
     state_current = AbstractMCMC.updatestate!!(
-        state.states[i], state.states[i_prev], state.transition
+        model, state.states[i], state.states[i_prev], state.transition
     )
 
     # Take a `step` for this sampler using the updated state.
@@ -217,7 +217,7 @@ end
 Suppose we then wanted to use this with some of the packages which implements AbstractMCMC.jl's interface, e.g. [`AdvancedMH.jl`](https://github.com/TuringLang/AdvancedMH.jl), then we'd simply have to implement `realize` and `realize!!`:
 
 ```julia
-function AbstractMCMC.updatestate!!(::AdvancedMH.Transition, state_prev::AdvancedMH.Transition)
+function AbstractMCMC.updatestate!!(model, ::AdvancedMH.Transition, state_prev::AdvancedMH.Transition)
     # Let's `deepcopy` just to be certain.
     return deepcopy(state_prev)
 end

src/AbstractMCMC.jl

@@ -80,14 +80,16 @@ The `MCMCSerial` algorithm allows users to sample serially, with no thread or pr
 struct MCMCSerial <: AbstractMCMCEnsemble end
 
 """
-    updatestate!!(state, transition_prev[, state_prev])
+    updatestate!!(model, state, transition_prev[, state_prev])
 
-Return new instance of `state` using information from `transition_prev` and, optionally, `state_prev`.
+Return new instance of `state` using information from `model`, `transition_prev` and, optionally, `state_prev`.
 
 Defaults to `realize!!(state, realize(transition_prev))`.
 """
-updatestate!!(state, transition_prev, state_prev) = updatestate!!(state, transition_prev)
-updatestate!!(state, transition) = realize!!(state, realize(transition))
+function updatestate!!(model, state, transition_prev, state_prev)
+    return updatestate!!(state, transition_prev)
+end
+updatestate!!(model, state, transition) = realize!!(state, realize(transition))
 
 """
     realize!!(state, realization)