20.3 Application: reimplementing source()

What do we need?

• Read the file being sourced.
• Parse its expressions (quote them?)
• Evaluate each expression saving the results
• Return the results

source2 <- function(path, env = caller_env()) {
  file <- paste(readLines(path, warn = FALSE), collapse = "\n")
  exprs <- parse_exprs(file)

  res <- NULL
  for (i in seq_along(exprs)) {
    res <- eval(exprs[[i]], env)
  }

  invisible(res)
}

The real source is much more complex.