functional-programming

问题 I have built a y-combinator in js like this const y = f => { const g = self => x => f(self(self))(x); return g(g);} and I simplified this code like this const y = f => { const g = self => f(self(self)); return g(g);} this get an infinite recursion. What's the difference between these two versions? 回答1: If you don't understand the difference between the two, I would be surprised that you actually built them. Nevertheless, perhaps the best way to demonstrate the difference between the two, is

问题 I'm having trouble deciphering the following function. Particularly, the flatMap line - where are the 'aa' and 'bb; variables coming from, and how is this executed? Maybe if someone could explain in words what is happening with this code it would be helpful. I'm just really struggling how to read this syntax. def map2[EE >: E, B, C](b: Either[EE, B])(f: (A, B) => C): Either[EE, C] = this flatMap(aa => b map (bb => f(aa, bb))) Here is the flatMap function: def flatMap[EE >: E, B](f: A =>

问题 I have functions which allow the user to compare two teams contained within a map. The data contained in the map is read in from a text file which contains information about football teams and their points tallies for the past 5 seasons. The data is stored as Map[String, List[Int]]: Manchester United, 72, 86, 83, 90, 94 Manchester City, 80, 84, 91, 77, 88 Chelsea, 76, 85, 92, 87, 84 Arsenal, 70, 79, 81, 76, 83 Liverpool, 69, 77, 80, 73, 79 The functions below allow the user to enter the names

问题 Im trying to install Oracle Applications Testing Suite - OpenScript, Helper Services are not getting installed. Getting Error when I run this Script - C:\OracleATS\OpenScript\InatallBrowserHelpers: WebDom Browser Helper Installation failed! Cannot save multiuser execution setting for Chrome native in registry under key: "HKLM\software\Google\Chrome\NativeMessagingHosts\oracle.openscript.host" Once open Script installed, Trying to run a simple Script, getting this Error: oracle.oats.scripting

问题 Background: Composition is putting two functions together to form a third function where the output of one function is the input of the other. No matter how much I look at this I struggle with how to read it. In particular why the compose() return => (a) => captures the 121.2121212 in local scope. Also I struggle with how final fn f(g(a)) would look with all the values/fn present w/o the use of variables. Question: Does anyone have any techniques or diagrams for quickly reading examples like

问题 I made a record called automaton containing the 5 fields required to represent an automaton I'm supposed to use graphics to represent every state and transition from the transitions list without using for or while loops only recursive functions transitions :(int*char*int) list; 回答1: It might be easiest to use graphviz to do the actual drawing. It automatically draws a graph from a list of nodes and edges, which is exactly what your input is. The function fmt_transition generates one edge, the

问题 From what I have understood, scala treats val definitions as values. So, any instance of a case class with same parameters should be equal. But, case class A(a: Int) { lazy val k = { println("k") 1 } val a1 = A(5) println(a1.k) Output: k res1: Int = 1 println(a1.k) Output: res2: Int = 1 val a2 = A(5) println(a1.k) Output: k res3: Int = 1 I was expecting that for println(a2.k), it should not print k. Since this is not the required behavior, how should I implement this so that for all instances

问题 I have the following Problem, given this XML Datastructure: <level1> <level2ElementTypeA></level2ElementTypeA> <level2ElementTypeB> <level3ElementTypeA>String1Ineed<level3ElementTypeB> </level2ElementTypeB> ... <level2ElementTypeC> <level3ElementTypeB attribute1> <level4ElementTypeA>String2Ineed<level4ElementTypeA> <level3ElementTypeB> <level2ElementTypeC> ... <level2ElementTypeD></level2ElementTypeD> </level1> <level1>...</level1> I need to create an Entity which contain: String1Ineed and

问题 I have method eval which takes List of Function and arguments, currently I am writing case for every possible function. How can I write it more generic? implicit class Expression(p: Product) { def eval = p.productIterator.toList match { case (f: ((Any) => Any)) :: p1 :: Nil => f(p1) case (f: ((Any, Any) => Any)) :: p1 :: p2 :: Nil => f(p1, p2) case (f: ((Any, Any, Any) => Any)) :: p1 :: p2 :: p3 :: Nil => f(p1, p2, p3) } } def print = (x: Any) => println(">> " + x) def add = (x: Any, y: Any)

问题 I have method eval which takes List of Function and arguments, currently I am writing case for every possible function. How can I write it more generic? implicit class Expression(p: Product) { def eval = p.productIterator.toList match { case (f: ((Any) => Any)) :: p1 :: Nil => f(p1) case (f: ((Any, Any) => Any)) :: p1 :: p2 :: Nil => f(p1, p2) case (f: ((Any, Any, Any) => Any)) :: p1 :: p2 :: p3 :: Nil => f(p1, p2, p3) } } def print = (x: Any) => println(">> " + x) def add = (x: Any, y: Any)