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export const getTodosState = state => state.todos;

export const getVisibiltyFilterState = state => state.visibilityFilter;

export const getVisibleTodos = createSelector(getTodosState, getVisibiltyFilterState, calcVisibleTodos);

function calcVisibleTodos( todos, filter ) {
  console.log('---------Recalculate todos---------');
}

// In your component
this.visibleTodos$ = this.store.select(fromRoot.getVisibleTodos);