[Rd] Conventions: Use of globals and main functions

[Cyclic Group Z_1]

> That beeing said I think the main task of scripts is to get things done via running them end to end in a fresh session. Now, it very well may happen that a lot of stuff has to be done. Than splitting up scripts into subscripts and sourcing them from a meta script is a straightforward solution. It might also be that some functionality is put into functions to be reused in other places. This can be done by putting those function definitions into separate files. Than one cane use source wherever those functions are needed. Now, putting stuff that runs code and scripts that define/provovide functions into the same script is a bad idea. Using the main()-idioms described might prevent this the problems stemming from mixing functions and function execution. But it would also encourage this mixing which is - I think, a bad idea anyways. 

I actually would agree entirely that files should not serve as both source files for re-used functions as well as application code. The suggestion for a main() idiom is merely to reduce variable scope and bring R practices more in line with generally recommended programming practices, not so that they can act as packages/modules/libraries. When I compared R scripts containing main functions to packages, I only mean in the sense that they help manage scope (the latter through package namespaces). Any other named functions besides main would be functions specifically tied to the script. 

I do see your point, though, that this could result in bad practice, namely the usage mixing you described. 

Best,
CG