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sealed class Event {
    object Increment : Event()
    object Decrement : Event()
}

data class State(
    val counter: Int = 0
)

class ViewModel {

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class ViewModel {

    private val events = Channel<Event>()

    val state = MutableStateFlow(State())

    init {
        events.receiveAsFlow()
            .onEach(::updateState)
            .launchIn(viewModelScope)

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class ViewModel {

    private val events = Channel<Event>()

    val state = events.receiveAsFlow()
        .runningFold(State(), ::reduceState)
        .stateIn(viewModelScope, Eagerly, State())

    fun handleEvent(event: Event) {
        events.trySend(event)

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interface StateReducerFlow<STATE, EVENT> : StateFlow<STATE> {
    fun handleEvent(event: EVENT)
}

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private class StateReducerFlowImpl<STATE, EVENT>(
    initialState: STATE,
    reduceState: (STATE, EVENT) -> STATE,
    scope: CoroutineScope
) : StateReducerFlow<STATE, EVENT> {

    private val events = Channel<EVENT>()

    private val stateFlow = events
        .receiveAsFlow()

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fun <STATE, EVENT> ViewModel.StateReducerFlow(
    initialState: STATE,
    reduceState: (STATE, EVENT) -> STATE,
): StateReducerFlow<STATE, EVENT> = StateReducerFlowImpl(initialState, reduceState, viewModelScope)

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class ViewModel {

    val state = StateReducerFlow(
        initialState = State(),
        reduceState = ::reduceState
    )

    private fun reduceState(currentState: State, event: Event): State {
        return when (event) {
            is Increment -> currentState.copy(counter = currentState.counter + 1)

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class ExampleActivity : Activity() {

    private val viewModel = ViewModel()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel.state.handleEvent(ExampleEvent)
    }
}

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@Composable
fun <ITEM, KEY> AnimatedVerticalGrid(
    items: List<ITEM>,
    itemKey: (ITEM) -> KEY,
    columns: Int,
    rows: Int
) 

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val itemSize = remember(columns, rows) {
    val itemWidth = (maxWidth) / rows
    val itemHeight = (maxHeight) / columns
    DpSize(itemWidth, itemHeight)
}