Macro r_str 

macro_rules! r_str {
    ($code:expr $(,)?) => { ... };
    ($code:expr, env = $env:expr $(,)?) => { ... };
}

Parse and evaluate runtime R source from Rust.

r_str! is sugar around expression::r_eval_str. It is the right tool when the R code is genuinely dynamic — built with format!, derived from user input, or otherwise not known at compile time. For code you can write literally, prefer r!, which gives a cheap compile-time sanity check on the token stream.

The argument is any expression evaluating to something AsRef<str> (&str, String, &String, …). It is parsed with R_ParseVector and evaluated with Rf_eval, with every intermediate SEXP protected and the parse status checked, so a syntax error becomes an Err, never a segfault or silent wrong answer.

Forms

• r_str!(code) — evaluate in R_GlobalEnv.
• r_str!(code, env = e) — evaluate in the environment SEXP e.

Both forms evaluate to Result<SEXP, String>; the SEXP is unprotected (protect it before further allocations).

Safety

Expands to an unsafe block. Must be reached from (or routed to) the R main thread — the underlying FFI is #[r_ffi_checked], so calls from a worker thread are serialized onto the R thread.

Example

let obj = "mtcars";
let code = format!("summary({obj})");
let summary = r_str!(&code)?;          // in R_GlobalEnv
let three = r_str!("1L + 2L")?;
let in_env = r_str!("x + 1", env = my_env)?;