Short answer For an integer range : Enumerable#sum returns (range.max-range.min+1)*(range.max+range.min)/2 Enumerable#inject(:+) iterates over every element. Theory The sum of integers between 1 and n is called a triangular number, and is equal to n*(n+1)/2. The sum of integers between n and m is the triangular number of m minus the triangular number of n-1, which is equal to m*(m+1)/2-n*(n-1)/2,
I have a local Git repository in ~/local_repo. It has a few branches: $ git branch * master rails c c++ To clone the local repository, I do: $ git clone ~/local_repo new_repo Initialized empty Git repository in /home/username/new_repo/.git/ The new_repo master branch points to the local_repo master branch, and I can push / pull. But I am unable to clone another branch. I want to only pull the bran
You can create an animated GIF using the Image I/O framework (which is part of the iOS SDK). You will also want to include the MobileCoreServices framework, which defines the GIF type constant. You need to add these frameworks to your target, and import their headers in the file where you want to create the animated GIF, like this: #import <ImageIO/ImageIO.h> #import <MobileCoreServices/MobileCore
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