[Suggestion] Name variables according to the fields

[wellguimaraes]

First of all, great project!

Currently, the variables are named v1, v2, v{n}... For the sake of debug, It'd be great if they're named after the fields. The variable "index" can be kept to grant uniqueness more easily (something like filter_1 instead of v1).

[wellguimaraes]

If the idea is welcome, I can work on a PR.