Function Rf_lang2 

pub unsafe fn Rf_lang2(s: SEXP, t: SEXP) -> SEXP

Build a language object (call) with function and 1 argument.

Rust equivalent of R’s inline Rf_lang2(s, t). Creates a call like f(arg) where s is the function and t is the argument.

Safety

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