Developer FAQs | Developer Questions And Answers

Confusion around when to compose, and when to use $

Given the above functions, I'm confused why let x = sumOfSquares . returnGreatest2 returnsbut sumOfSquares $ returnGreatest2 3 5 7 does the right thing. Since the type coming out of returnGreatest2 is the same as the type sumOfSquares expects, I would think I'd be able to compose them.

11月18日发表评论

Using fields stored in variadic data structure as method arguments

I have a variadic data structure, each "layer" containing one field.How can use all the fields stored in the structure as arguments to a function or a constructor?

11月18日发表评论

Count data divided by year and by region in R

I have a very large (too big to open in Excel) biological dataset that looks something like this What I am looking to do is figure out how many of each species (A, B, or C) exist in each region (1, 2, or 3) in each of the three years...

11月18日发表评论

C++ in condition

How to check if a value is in a on-the-fly created set. I'm looking for some syntactic sugar, like we have in python

11月18日发表评论

Error “Unable to use the video in an ad creative. Video id XXX,XXX,XXX,XXX,XXX might not be id of a video, or you might not have permission to see it”

I'm trying to create an ad using the php-facebook-sdk and with the help of curl Facebook API.I already have uploaded my video with the use of curl and it returns an id. Now, that video id will be used to add an adcreative, but when I submit my adcreative it...

11月17日发表评论

Why does O(n^2) code execute faster than O(n)?

I have written code for 2 approaches to find out the first unique character in a string on LeetCode.Problem Statement: Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

11月17日发表评论

Passing int[][] as generic parameter

I'm trying to pass a 2-dimensional array, int[][] arr.I cannot use func1(arr) , but I can use func2(arr)

11月17日发表评论

How to properly access mapped memory without undefined behavior in C++

I've been trying to figure out how to access a mapped buffer from C++17 without invoking undefined behavior. For this example, I'll use a buffer returned by Vulkan's vkMapMemory.

11月17日发表评论

Why does the compiler prefer f(const void*) to f(const std::string &)?

Consider the following piece of code:I compiled this program using g++ (Ubuntu 6.5.0-1ubuntu1~16.04) 6.5.0 20181026:

11月17日发表评论

Is it possible for `contains` to return non-boolean value?

The documentation says that __contains__ should return true if item is in self, false otherwise. However, if the method returns a non-boolean value x, it seems that python automatically converts it to bool(x).

11月17日发表评论