(Incomplete) simple module mechanism for R.

import.R

import <- function (module) {
    module <- as.character(substitute(module))
    # Search path handling omitted for simplicity.
    filename <- paste(module, 'R', sep = '.')

    includeGuard <- paste('.INCLUDE', toupper(module), 'R', sep = '_')
    if (exists(includeGuard))
        return()

    assign(includeGuard, TRUE, envir = topenv())
    sys.source(filename, chdir = TRUE)
}