idiomatic

问题 I've got a piece of aggregation code that works well enough but runs a bit slow against a data frame with 10e6 rows. I'm not that experienced in R so apologies for my cringe worthy code! I just want to do a basic roll up and sum of values for a common key... eg go from... key val 1 a 5 2 b 7 3 a 6 to... key val 1 a 11 2 b 7 the best i can manage is... keys = unique(inp$key) vals = sapply(keys, function(x) { sum(inp[inp$key==x,]$val) }) out = data.frame(key=keys, val=vals) I have this gut feel

问题 This question already has answers here : unpacking function argument [duplicate] (2 answers) Closed 5 years ago . I'm beginning to feel a little dumb for not figuring this out... say I have a function of two variables: def testfun(x,y): return x*y now I have a list of values, say [2,3] , which I want to input as values into the function. What's the most Pythonic way to do this? I thought of something like this: def listfun(X): X_as_strs = str(X).strip('[]') expression = 'testfun({0})'.format

问题 I am trying to convert a Python script into Rust as a learning experience and to make the tool faster and shrink the size of the code/executable. I'm currently trying to convert a section that creates a list of references to methods on self. Now I've learned that there isn't a way to bind the self variable for a method, one has to use a closure and close over the object that the methods will be called on. However when you create a closure it gets assigned a unique anonymous type, so I don't

问题 I am trying to split a string without regex in a more idiomatic functional approach. case class Parsed(blocks: Vector[String], block: String, depth: Int) def processChar(parsed: Parsed, c: Char): Parsed = { import parsed._ c match { case '|' if depth == 0 => parsed.copy(block = "", blocks = blocks :+ block , depth = depth) case '[' => parsed.copy(block = block + c, depth = depth + 1) case ']' if depth == 1 => parsed.copy( block = "", blocks = blocks :+ (block + c), depth = depth - 1) case ']'

问题 Woe is me, I have to ensure the same floating-point results on a GPU and on the CPU. Ok, I understand IEEE has taken care of me and provided a nice standard to adhere to with several rounding options; and the CUDA part is sorted out (there are intrinsics for the different rounding modes), so that's just motivation. But in host-side C++ code - how do I perform floating-point arithmetic in a specific rounding mode (and I mean in a specific statement, not throughout my translation unit)? Are

问题 Consider the following function: foo = [1,2,3] >>= return . (*2) . (+1) For better readability and logic, I would like to move my pure functions (*2) and (+1) to the left of the return. I could achieve this like this: infixr 9 <. (<.) :: (a -> b) -> (b -> c) -> (a -> c) (<.) f g = g . f bar = [1,2,3] >>= (+1) <. (*2) <. return However, I don't like the right-associativity of (<.) . Let's introduce a function leftLift : leftLift :: Monad m => (a -> b) -> a -> m b leftLift f = return . f baz =

问题 What is the idiomatic way for checking a value for zero in Python? if n == 0: or if not n: I would think that the first one is more in the spirit of being explicit but on the other hand, empty sequences or None is checked similar to the second example. 回答1: If you want to check for zero, you should use if n == 0 . Your second expression doesn't check for zero, it checks for any value that evaluates as false. I think the answer lies in your requirements; do you really want to check for zero,

问题 So, this question tells how to perform a list comprehension in R to filter out new values. I'm wondering, what is the standard R way of writing a list comprehension which is generating new values? Basically, if we have a function f and vector x , I want the list f(el) for el in x . (This is like map in functional programming). In Python, this would just be [f(el) for el in x] . How do I write this in R, in the standard way? The problem is, right now I have for-loops: result = c(0) for (i in 1

问题 Suppose I have a template <typename T> class A : class_with_long_name<T, and_many_other, template_arguments, oh_my_thats_long>, anotherclass_with_long_name<and_many_other, template_arguments_that, are_also_annoying, including_also, T> { ... } Now, in class A's definition, and/or in its methods, I need to refer to the two superclasses (e.g. to access members in the superclass, or types defined in it etc.) However, I want to avoid repeating the superclass names. At the moment, what I'm doing is

问题 I've read this and this, but I still don't understand the (idiomatic) equivalent way to do this in Scala enum Status { OK(1, "Ok", "Okay"), NOT_OK(5, "Not Ok", "Not Okay") BAD(10, "Bad", "Run for your life") int code; String name; String description; // custom fields Status(int code, String name, String description) { this.code = code; this.name = name; this.description = description; } } class Main { public static void main(String[] args) { for(Status status : Status.values) { // iterate