Function Rf_lang4 

pub unsafe fn Rf_lang4(s: SEXP, t: SEXP, u: SEXP, v: SEXP) -> SEXP

Build a language object (call) with function and 3 arguments.

Rust equivalent of R’s inline Rf_lang4(s, t, u, v). Creates a call like f(arg1, arg2, arg3).

Safety

• All SEXPs must be valid
• Must be called from R’s main thread
• Result must be protected from GC