The pseudo-type lumping closure, builtin and special
FUNSXP.Rd
FUNSXP is an object-like macro defining a FUNSXP
pseudo-type of lumping closure, builtin and special objects.
Declaration
#define FUNSXP 99 /* Closure or Builtin or Special */
In Rinternals.h.
References
https://cran.r-project.org/doc/manuals/r-patched/R-ints.html#SEXPTYPEs