The type of language constructs
LANGSXP.Rd
LANGSXP is an object-like macro defining the SEXPTYPE
type of language constructs such call and formula
objects.
Declaration
#define LANGSXP 6 /* language constructs (special lists) */
In Rinternals.h.
References
https://cran.r-project.org/doc/manuals/r-patched/R-ints.html#SEXPTYPEs