Function ALTREP 

pub unsafe fn ALTREP(x: SEXP) -> c_int

Check if a SEXP is an ALTREP object (returns non-zero if true).

Use SexpExt::is_altrep() instead of calling this directly. Checked wrapper for ALTREP. Calls ALTREP_unchecked and routes through with_r_thread. Generated from source location line 666, column 12. Generated from source file miniextendr-api/src/sys.rs.