Based on this answer, I learned of a special class of internal functions that can be accessed from R: a set of functions accessed via .Internal(specialFunction). If one queries ?.Internal this excerpt may be found:
Only true R wizards should even consider using this function, and only R developers can add to the list of internal functions.
I want to master potions and defense against the Dark Arts for my OWLs interesting R functions. Where can R wizards find a list and description of the internal functions? So long as it doesn't involve splitting my soul.
They're in src/main/names.c but they are not alone. The .Primitive are there too. And some dragons.
They are documented in Section 2) .Internal vs .Primitive in the R Internals manual.
来源：https://stackoverflow.com/questions/7327521/reference-for-r-wizards