Hey, Haskellers, I'm trying to use state threaded through an arrow in some HXT code to avoid passing explicit parameters through several layers of functions, but I think I'm not understanding quite what the arrow notation is doing, because when I try to use a value I'm extracting from the state, I'm getting a scope error. I had many ways I was prepared for the code to be wrong, but that one has me baffled. Any suggestions? Mike. {-# LANGUAGE Arrows, NoMonomorphismRestriction #-} module HXTTest () where import Text.XML.HXT.Core data Info = Info { value :: String } deriving (Show) info = Info { value = "foo" } html = "<html><head></head><body><div class='foo'>llama</div></body>"; -- print (runSLA (getState >>> arr value) info html) -- Div class is static, no reference to state findFoo = proc content -> do (deep (isElem >>> hasName "div" >>> hasAttrValue "class" (== "foo"))) -< content -- print (runSLA (hread >>> findFoo) info html) -- Extract class from state, but don't use it findFoo' = proc content -> do divName <- (getState >>> arr value) -< content content >- (deep (isElem >>> hasName "div" >>> hasAttrValue "class" (== "foo"))) -- print (runSLA (hread >>> findFoo') info html) -- Extract class from state, try to use it: "Not in scope: `divName'" -- findFoo'' = -- proc content -> do -- divName <- (getState >>> arr value) -< content -- content >- (deep (isElem >>> -- hasName "div" >>> -- hasAttrValue "class" (== divName)))