This is an example of a library. You may see a list of other libraries used on Rosetta Code at Category:Solutions by Library.
Wren-vector is a module which adds support for manipulation of geometric vectors to the Wren programming language. It consists of 3 classes: Vector, Vector2 and Vector3 which represent generic n-dimensional and specialized two and three dimensional vectors respectively.
It is the forty-third in a series of modules (listed on the language's main page) designed to assist with writing Rosetta Code tasks so the same code does not have to be written or copy/pasted time and time again thereby bloating a task's script code unnecessarily.
To use it you need to copy the source code (in the talk page) to a text file called vector.wren and place this in the same directory as the importing script so the command line interpreter can find it.