state

问题 How does history management work in GHCI or other Haskell-based REPLs? Since Haskell is a pure language, I guess it's implemented using a monad, perhaps the state monad. Kindly note I'm a beginner in Haskell, so please provide a detailed explanation rather than just linking to the source. 回答1: This is a simplified example of how a program might keep a history of commands entered by the user. It basically has the same structure as the number guessing game, so once you understand that you

问题 How does history management work in GHCI or other Haskell-based REPLs? Since Haskell is a pure language, I guess it's implemented using a monad, perhaps the state monad. Kindly note I'm a beginner in Haskell, so please provide a detailed explanation rather than just linking to the source. 回答1: This is a simplified example of how a program might keep a history of commands entered by the user. It basically has the same structure as the number guessing game, so once you understand that you

问题 I am trying to work out a data structure for the following situation. Graph Structure I plan to have a graph of nodes with un-weighted, directed edges: Graph = [Node] Each node has: Some TBD internal (persistent) state A queue of incoming messages A type of message it can send determined by a function that accepts the current node state (with the possibility of failure) A list of edges Node { nodeState :: NodeState, inbox :: Queue NodeMessage, nodeMessage :: (NodeState -> Maybe NodeMessage),

问题 I am trying to work out a data structure for the following situation. Graph Structure I plan to have a graph of nodes with un-weighted, directed edges: Graph = [Node] Each node has: Some TBD internal (persistent) state A queue of incoming messages A type of message it can send determined by a function that accepts the current node state (with the possibility of failure) A list of edges Node { nodeState :: NodeState, inbox :: Queue NodeMessage, nodeMessage :: (NodeState -> Maybe NodeMessage),

问题 Assume my table is this I am trying to modify my table with this information I have added two columns where column WhenWasLastBasicSubjectDone will let you know when in which semester the student completed his latest Basic Course (sorted by Semester). The other column TotalBasicSubjectsDoneTillNow explains how many times had the student completed Basic Course(Subject) till now (sorted by Semester) ? I think this is easy to solve with Joins as well as with UDFs but I want to use the power of

问题 Recently, I have encountered many difficulties when I was developing using C++ and Lua. My situation is: for some reason, there can be thousands of Lua-states in my C++ program. But these states should be same just after initialization. Of course, I can do luaL_loadlibs() and lua_loadfile() for each state, but that is pretty heavy(in fact, it takes a rather long time for me even just initial one state). So, I am wondering the following schema: What about keeping a separate Lua-state(the only

问题 I'm unsure how I'm supposed to save the game state of my game that I'm developing. Should I save a instance/object containing all the game information? If yes, how? Or should I save all the relative information in a .txt file and save/load information when needed? How do you do this and what do you think of my proposals? 回答1: You can't save an Instance / Object unless you serialize it and save it to some text/binary/database file. Your two options are kind of identical therefore. What you

问题 I am trying to create a scopedmodel in my flutter project and I can't seem to figure out why I get the error. What is wrong in this scopedmodel implementation? I have a home page with bottom navigator. Inside the profile tab, I fetch the list of followers which I need in a widget deep in the tree so I am trying to use scopedmodel. The model code is class RelationshipsModel extends Model { List<Relationship> relations; RelationshipsModel(this.relations); void add(String name) { relations.add

问题 So I have an image button and I want to have two states on it. It will work like a bookmark button which has two states. If the user presses the button then it changes the image and if it re-presses the button then I want the original image back. Is that possible? Is there an easier way using another type of button? Thank you 回答1: Try changing the topic to :"What kind of Button can toggle/change states?" Seems like you need ToggleBotton <ToggleButton android:layout_width="wrap_content"

问题 I need to be able to save the state of a Centos-based Google Compute instance when it first receives a preemption signal. The documentation very clearly indicates that a "ACPI G2 Soft Off" signal is sent 30 seconds before a preemptible shutdown. Unfortunately, Google has given no examples to demonstrate how to capture this signal and I have not yet found a way to capture it. My initial attempts have all been focused around the ACPI Interface using the acpid daemon. Using it, I have been able