Re: [Rd] Conventions: Use of globals and main functions

[Cyclic Group Z_1 via R-devel]

This is a fair point; structuring functions into packages is probably 
ultimately the gold standard for code organization in R. However, lexical 
scoping in R is really not much different than in other languages, such as 
Python, in which use of main functions and defining other named functions 
outside of main are encouraged. For example, in Scheme, from which R derives 
its scoping rules, the community generally organizes code with almost 
exclusively functions and few non-function global variables at top level. The 
common use of globals in R seems to be mostly a consequence of historical 
interactive use and, relatedly, an inherited practice from S.

It is true, though, that since anonymous functions (such as in lapply) play a 
large part in idiomatic R code, as you put it, "[l]exical scoping means that 
all of the problems of global variables are available to writers who use 
main()." Nevertheless, using a main function with other functions defined 
outside it seems like a good quick alternative that offers similar advantages 
to making a package when functions are tightly coupled to the script and the 
project may not be large or generalizable enough to warrant making a package.

Best,
CG

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