currying

问题 Say I want to implement a numerical integration routine with plain C. That will look something like this: double integrate(double (*f)(double), double lower, double upper, double step)); I often find functions that actually depend on multiple variables, and I want to integrate over the first one. Say I want to integrate this: double func(double x, double z); with respect to x . I cannot pass func to integrate since it has the wrong signature. Now I know the following workarounds, which were

问题 Could someone please explain the concept of currying to me. I am primarily learning it because we are learning ML in my 'modern programming language' class for a functional language introduction. In particular you can use this example: -fun g a = fn b => a+b; val g = fn: int -> int -> int -g 2 3; val it = 5 : int I'm confused how these parameters are passed or how to even think about it in the first place. Thank you for any help. 回答1: In this case, you make the currying explicit, so it should

问题 I'm reading a book, Functional Programming Using F#, which says (page 33), in the section Declaration of higher-order functions We have seen higher-order built-in functions like (+) and (<<) and at the end of the section Higher-order functions may alternatively be defined by supplying the arguments as follows in the let-declaration: let weight ro s = ro * s ** 3.0;; However there were some helpful comments at the bottom of a question that I asked earlier today (which was originally titled

问题 is that possible to pipe the first parameter into a multiple parameter function? for example date = "20160301" Is that possible to pipe date into DateTime.ParseExact( , "yyyyMMDD", CultureInfo.InvariantCulture) 回答1: As @yuyoyuppe explains in his/her answer, you can't pipe directly into ParseExact because it's a method, and thereby not curried. It's often a good option to define a curried Adapter function, but you can also pipe into an anonymous function if you only need it locally: let res =

问题 "Introduction to Caml" says Note, in Caml it is better to use Curried function definitions for multiple-argument functions, not tuples. when comparing 'a -> 'b -> 'c calling conventions to 'a * 'b -> 'c . When working with SML/NJ I got used to using tuple types for both input and output : ('a * 'b) -> ('c * 'd) so using tuples to express multiple inputs seems symmetric with the way I express multiple outputs. Why is currying recommended for OCaml function declarations over tuple arguments? Is

问题 I recently started coding in Python and I was wondering if it's possible to return a function that specializes another function. For example, in Haskell you can create a function that adds 5 to any given number like this: sumFive = (+5) Is it somehow possible in Python? 回答1: I think the other answers are misunderstanding the question. I believe the OP is asking about partial application of a function, in his example the function is (+) . If the goal isn't partial application, the solution is

问题 Trying to figure out why the code compiles for nested type inference on method with arity-2 but not with currying. object Test { trait Version object VersionOne extends Version trait Request[A <: Version] trait RequestOne extends Request[VersionOne.type] case class HelloWorld() extends RequestOne def test1[A <: Version, T <: Request[A]](t : T, a : A): T = t def test2[A <: Version, T <: Request[A]](t : T)(a : A): T = t } // This works Test.test1(Test.HelloWorld(), Test.VersionOne) // This

问题 Programming in Haskell by Hutton says When evaluating an expression, in what order should the reductions be performed? One common strategy, known as innermost evaluation , is to always choose a redex that is innermost, in the sense that it contains no other redex. If there is more than one innermost redex, by convention we choose the one that begins at the leftmost position in the expression. Another common strategy for evaluating an expression, dual to innermost evaluation, is to always

问题 In my urlconf, i have: url(r'^sssssh/(.*)', staff_only_app.site.root), What I'd like to do is limiting any access to this application to superusers. I tried this: url(r'^sssssh/(.*)', user_passes_test(staff_only_app.site.root, lambda u: u.is_superuser)), But it complains that decorate takes exactly 1 argument, and I gave two. I'm thinking about currying the decorator via functools.partial, but thought I may be missing some more obvious solution. 回答1: Very late reply!... I think it's just a

问题 I came across some code in scala in a similar form like this: def test1(f : Int => Int)(x : Int) = x + f(x) def test2(f : Int => Int)(x : Int) = f(x) test2(test1(x => 2*x))(2) I'm confused, so function test1 takes a function and a Int as parameters, and returns a function, right? Then how can test1(x => 2*x) be valid and returns a function to test2? Apparently it takes 2 asthe integer parameter, but why? How does the statement test2(test1(x => 2*x))(2) expand? Thanks in advance. 回答1: This: