partial-application

问题 This question already has answers here : Overriding special methods on an instance (5 answers) Closed last year . I have a couple classes and a function: from functools import partial def fn(other, self, name): print(f"calling {name} with {other}") func = getattr(self.a, name) return func(other) class A: def __add__(self, other): return 9 def __mul__(self, other): return 7 def __sub__(self, other): return 8 class B: def __init__(self,a): self.a = a for name in ['add', 'sub']: name = f"__{name

问题 This question already has answers here : Overriding special methods on an instance (5 answers) Closed last year . I have a couple classes and a function: from functools import partial def fn(other, self, name): print(f"calling {name} with {other}") func = getattr(self.a, name) return func(other) class A: def __add__(self, other): return 9 def __mul__(self, other): return 7 def __sub__(self, other): return 8 class B: def __init__(self,a): self.a = a for name in ['add', 'sub']: name = f"__{name

问题 This question already has answers here : Overriding special methods on an instance (5 answers) Closed last year . I have a couple classes and a function: from functools import partial def fn(other, self, name): print(f"calling {name} with {other}") func = getattr(self.a, name) return func(other) class A: def __add__(self, other): return 9 def __mul__(self, other): return 7 def __sub__(self, other): return 8 class B: def __init__(self,a): self.a = a for name in ['add', 'sub']: name = f"__{name

问题 In Python, is it considered better style to: explicitly define useful functions in terms of more general, possibly internal use, functions; or, use partial function application to explicitly describe function currying? I will explain my question by way of a contrived example. Suppose one writes a function, _sort_by_scoring, that takes two arguments: a scoring function and a list of items. It returns a copy of the original list sorted by scores based on each item's position within the original

问题 Can you pass in an operation like "divide by 2" or "subtract 1" using just a partially applied operator, where "add 1" looks like this: List.map ((+) 1) [1..5];; //equals [2..6] // instead of having to write: List.map (fun x-> x+1) [1..5] What's happening is 1 is being applied to (+) as it's first argument, and the list item is being applied as the second argument. For addition and multiplication, this argument ordering doesn't matter. Suppose I want to subtract 1 from every element (this

问题 Wondering if you can comment on why following two scenarios behave differently: The following works: var la= List(12, 13 , 14 ,15); var func = (x:Int) => println(x) la.foreach(func) // 1 la.foreach(func(_)) // 2 But the following does not: var la= List(12, 13 , 14 ,15); var func1 = (x:Int) => { for (i <- 0 to x) yield i*2 } mkString la.foreach(println(func1)) // similar to 1 above la.foreach(println(func1(_))) // similar to 2 above error: type mismatch; found : Unit required: Int => ? la

问题 map2_List :: (a -> b -> c) -> [a] -> [b] -> [c] map2_List f [] _ = [] map2_List f (a:as) bs = map (f a) bs ++ map2_List f as bs This is an example from my lecture, which try to apply a binary function to all pairs of elements of two lists. The part (f a) makes me confused. Does it suppose to be a value but not a function? Then what does map value bs do? 回答1: "The part (f a) makes me confused." What is happening here is called currying and if you are coming to Haskell from imperative languages

问题 I started learning Haskell and found a nice exercise. It's the following: grouping: Int -> [Student]->[(Team, Student)] grouping teamNumber = zip ys where ... So, the exercise wants that i try to fill the rest. The function should do the following: Example : grouping 2 ['Mark','Hanna','Robert','Mike','Jimmy'] = [(1,'Mark'),(2,'Hanna'),(1,'Robert'),(2,'Mike'),(1,'Jimmy')] . So, we are building teams which consists of two Students, and the last Student 'Jimmy' has no teammates. Then, I also

问题 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

问题 I'm a bit shaky on the rules as to when you need a _ after a method to use it as a function. For example, why is there a difference between Foo 's and Nil 's :: in the following? def square(n: Int) = n * n object Foo { def ::(f: Int => Int) = f(42) } // ... scala> Foo.::(square) res2: Int = 1764 scala> Nil.::(square) <console>:6: error: missing arguments for method square in object $iw; follow this method with `_' if you want to treat it as a partially applied function Nil.::(square) ^ scala>