This Pull Request is for HacktoberFest 2020

Description of Change

Checklist

• Added description

Add quickselect algorithm. Quickselect is a selection algorithm to find the kth smallest element in an unordered list.

Welcome to JavaScript community

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that p

Description of Change

References

Checklist

Currently we've implemented a bunch of functions and constraints in a "lazy evaluation" fashion, i.e., whenever we need something for a Style program, we implement it in Penrose. We're getting to the point where we should really have a more complete/comprehensive list (e.g., that users can call at will).

How do we come up with this list? One natural idea is to simply pick some libraries, and

RDF::Mean() uses plain doubles. That's better than float, but far from stable. When you run with IMT, it's actually more accurate than without, because less numbers go into one accumulator, and each running sum remains smaller. So IMT/NoIMT can break your tests (even different TBB scheduling does).

It was creating problems already in this simple test (note that the precision threshold for tes

What is the feature or improvement you would like to see?
Two qsort-compatible functions that can do lexicographic comparison of igraph_vector_(whatever)_t objects. One should do it the standard way, the other should effectively consider the reverse of each vector.

Use cases for the feature
Canonicalizing the output of some functions, canonicalizing results in unit tests.

Why t