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I've put together a class that gives similar functionality in Lua for what Linq let's you do in C#. Most anyone who's worked with C# fairly recently is probably somewhat familiar with Linq and the lambda notation that works with it. It pretty much comes down to being able to query and work with collections with similar constructs like you can in SQL (ie. select, where, aggregate functions).
Here's a snippet from my example program below that hopefully gives a general idea of how my class works in Lua.
nyEmpCities = emps:where(function(e) return e.address.state == "NY" end): select(function(e) return e.address.city end):distinct()
emps is a previously populated collection that is of the type of my new class: LinqArray. It holds employee info for a number of employees. That snippet shows how to pull out the employees that live in NY, then pulls out the cities each of those employees live in, and lastly returns just a distinct list of those cities in NY and stores it in another variable.
There are a decent number of methods included with the LinqArray class: min, max, sum, avg, removeWhere, along with the core ones above and a few others.
I know working in C# being able to query and work with collections with Linq greatly reduces the amount of code I have to write. I just figured having a similar library in Lua would be useful. In no way is that class optimized and there are probably some bugs in it.
http://pastebin.com/gKzxTCtp is the LinqArray class.
http://pastebin.com/3ig2FmVN is an example program that uses the LinqArray class. It just prints output, but the code should be fairly straight forward to understand.