gistfile1.txt

-- Simple example: WORKS

followSplit : Mod -> Mod
followSplit oldMod =
    let
        newTransformer : Node -> Node
        newTransformer node =
            case node of
                Split nodes ->
                    let
                        newNodes : List Node
                        newNodes =
                            List.map newTransformer nodes
                    in
                    Split newNodes

                _ ->
                    oldMod.transformer node
    in
    { oldMod | transformer = newTransformer }
    
-- Real example: DOESN'T WORK

includeVariableEffects : Mod -> Mod
includeVariableEffects mod =
    let
        transformer =
            mod.transformer

        newTransformer : Int -> Effect -> Effect
        newTransformer =
            \multiplier effect ->
                case getType effect of
                    VariableSuccess { successProbability, successEffects, failureEffects } ->
                        let
                            ( successEffectsDidChange, newSuccessEffects ) =
                                let
                                    newEffects : List Effect
                                    newEffects =
                                        List.concatMap (applyModsToEffect 0 [ { mod | transformer = newTransformer multiplier } ]) successEffects
                                in
                                ( successEffects /= newEffects, newEffects )

                            ( failureEffectsDidChange, newFailureEffects ) =
                                let
                                    newEffects : List Effect
                                    newEffects =
                                        List.concatMap (applyModsToEffect 0 [ mod ]) failureEffects
                                in
                                ( failureEffects /= newEffects, newEffects )

                            effectDidChange =
                                successEffectsDidChange || failureEffectsDidChange
                        in
                        if effectDidChange then
                            effect
                                |> setType
                                    (VariableSuccess
                                        { successProbability = successProbability
                                        , successEffects = newSuccessEffects
                                        , failureEffects = newFailureEffects
                                        }
                                    )
                                |> ChangeEffect

                        else
                            NoChange

                    _ ->
                        transformer multiplier effect
    in
    { mod | transformer = newTransformer }