struct SEXPREC
The struct SEXPREC seems to be the container for a value.
typedef struct SEXPREC {
SEXPREC_HEADER;
union {
struct primsxp_struct primsxp;
struct symsxp_struct symsxp;
struct listsxp_struct listsxp;
struct envsxp_struct envsxp;
struct closxp_struct closxp;
struct promsxp_struct promsxp;
} u;
} SEXPREC;
A pointer type is also defined that points to a SEXPREC:
typedef struct SEXPREC *SEXP;
SEXPTYPE
typedef enum {
NILSXP = 0, /* nil = NULL */
SYMSXP = 1, /* symbols */
LISTSXP = 2, /* lists of dotted pairs */
CLOSXP = 3, /* closures */
ENVSXP = 4, /* environments */
PROMSXP = 5, /* promises: [un]evaluated closure arguments */
LANGSXP = 6, /* language constructs (special lists) */
SPECIALSXP = 7, /* special forms */
BUILTINSXP = 8, /* builtin non-special forms */
CHARSXP = 9, /* "scalar" string type (internal only)*/
LGLSXP = 10, /* logical vectors */
INTSXP = 13, /* integer vectors */
REALSXP = 14, /* real variables */
CPLXSXP = 15, /* complex variables */
STRSXP = 16, /* string vectors */
DOTSXP = 17, /* dot-dot-dot object */
ANYSXP = 18, /* make "any" args work */
VECSXP = 19, /* generic vectors */
EXPRSXP = 20, /* expressions vectors */
BCODESXP = 21, /* byte code */
EXTPTRSXP = 22, /* external pointer */
WEAKREFSXP = 23, /* weak reference */
RAWSXP = 24, /* raw bytes */
S4SXP = 25, /* S4 non-vector */
NEWSXP = 30, /* fresh node creaed in new page */
FREESXP = 31, /* node released by GC */
FUNSXP = 99 /* Closure or Builtin */
} SEXPTYPE;