partial-application

Haskell partial function application with $

由 徘徊边缘 提交于 2019-12-10 15:49:14
问题 I'm new to Haskell and looking at a simple example of using function application with $ . It seems straightforward - it takes a function and applies it to a value. So this makes sense: > (+3) $ 2 5 This also makes sense: > ($) (+3) 2 5 This makes sense because the first argument is the function, and the second argument is the value. Now considering using $ to create a partial function. Looking at types, this makes sense - it just needs a Num type value for b : > :t ($) (+3) ($) (+3) :: Num b

What is the best pattern to curry delegate parameters (using .NET 2.0 or later)?

由 橙三吉。 提交于 2019-12-10 02:17:17
问题 Sometimes it is useful to take a method call, complete with parameters, and turn it into a MethodInvoker which will invoke the indicated function with those parameters, without having to specify the parameters at the time. At other times, it's useful to do something similar, but leaving some parameters open. This type of action is called "Currying". What is the best pattern for doing this in VB? It's possible to use lambda expressions in VB 2010, but lambda expressions aren't compatible with

Partial Application with Infix Functions

由 给你一囗甜甜゛ 提交于 2019-12-10 01:34:57
问题 While I understand a little about currying in the mathematical sense, partially applying an infix function was a new concept which I discovered after diving into the book Learn You a Haskell for Great Good. Given this function: applyTwice :: (a -> a) -> a -> a applyTwice f x = f (f x) The author uses it in a interesting way: ghci> applyTwice (++ [0]) [1] [1,0,0] ghci> applyTwice ([0] ++) [1] [0,0,1] Here I can see clearly that the resulting function had different parameters passed, which

Partial application in Haskell with multiple arguments

由 纵然是瞬间 提交于 2019-12-09 18:48:11
问题 Given some function f(x1,x2,x3,..,xN) it is often useful to apply it partially in several places. For example, for N=3 we could define g(x)=f(1,x,3). However, the standard partial application in Haskell does not work this way and only allows us to partially apply a function by fixing its first arguments (because all functions actually only take one argument). Is there any simple way to do something like this: g = f _ 2 _ g 1 3 with output the value of f 1 2 3 ? Of course we could do a lambda

Haskell - Currying? Need further explanation

由 僤鯓⒐⒋嵵緔 提交于 2019-12-09 13:13:18
问题 So something like addList :: [int] -> int addList = foldl1 (+) Why does this work? The Currying part. Why no variable? 回答1: If you define a function like f x y = bla , this is the same as f x = \y -> bla , which is the same as f = \x -> (\y -> bla) . In other words f is a function which takes one argument, x , and returns another function which takes one argument, y , and then returns the actual result. This is known as currying. Analogously when you do f x y , it's the same as (f x) y . I.e.

Privacy in JavaScript

由 青春壹個敷衍的年華 提交于 2019-12-08 21:37:52
问题 Function scoping offers the only privacy in JavaScript. So the canonical: function Ctor(dep1, dep2) { this._dep1 = dep1; this._dep2 = dep2; } Ctor.prototype.foo = function() { // use this._dep1/2... } ...is problematic in that it offers no encapsulation for the injected dependencies. An alternative (albeit slightly different in terms of location of foo ) that offers real encapsulation might be: function factory(dep1, dep2) { return { foo: partial(foo, dep1, dep2), // or use bind (partial

When (if ever) can type synonyms be partially applied?

由 走远了吗. 提交于 2019-12-08 15:15:19
问题 Apparently a bit absent-mindedly, I wrote something like the following: {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TypeFamilies #-} class Foo f where type Bar f :: * retbar :: Bar f -> IO f type Baz f = (Foo f, Eq f) -- WithBar :: * -> (*->Constraint) -> * -> Constraint type WithBar b c f = (c f, Bar f ~ b) instance Foo () where type Bar () = () retbar = return naim :: WithBar () Baz u => IO u -- why can I do this? naim = retbar () main = naim :: IO () Only after successfully compiling, I

What is the best pattern to curry delegate parameters (using .NET 2.0 or later)?

由 自作多情 提交于 2019-12-05 01:13:51
Sometimes it is useful to take a method call, complete with parameters, and turn it into a MethodInvoker which will invoke the indicated function with those parameters, without having to specify the parameters at the time. At other times, it's useful to do something similar, but leaving some parameters open. This type of action is called "Currying". What is the best pattern for doing this in VB? It's possible to use lambda expressions in VB 2010, but lambda expressions aren't compatible with edit-and-continue, and the closures they create can have unexpected by-reference behaviors. An

Partial Application with Infix Functions

由 戏子无情 提交于 2019-12-05 00:31:50
While I understand a little about currying in the mathematical sense, partially applying an infix function was a new concept which I discovered after diving into the book Learn You a Haskell for Great Good . Given this function: applyTwice :: (a -> a) -> a -> a applyTwice f x = f (f x) The author uses it in a interesting way: ghci> applyTwice (++ [0]) [1] [1,0,0] ghci> applyTwice ([0] ++) [1] [0,0,1] Here I can see clearly that the resulting function had different parameters passed, which would not happen by normal means considering it is a curried function (would it?). So, is there any

Partial Application - Eloquent Javascript

由 匆匆过客 提交于 2019-12-04 15:43:03
I am reading Eloquent Javascript and am having a difficult time understand the example below. Would anyone be able to do a line by line type explanation? Specifically, I'm confused as to why the first loop is starting at one, and why the push method is being used on both knownArgs and arguments. I know that this is related to "partial application", but would like a more detailed explanation of what exactly is happening line by line. var op = { "+": function(a,b){return a + b;} }; function partial(func) { var knownArgs = arguments; return function() { var realArgs = []; for (var i=1; i
订阅 partial-application