Calling R function from C

00README.md

This is an example of C code calling an R function, by building a function call and then evaluating it.

checkver.R

library(inline)

checkver <- cfunction(
  body = '
  SEXP e, ret;
  bool result;

  // This is the expression `packageVersion("later") >= "0.8.0.9003"`
  e = PROTECT(
    Rf_lang3(
      Rf_install(">="),
      Rf_lang2(Rf_install("packageVersion"), Rf_mkString("later")),
      Rf_mkString("0.8.0.9003")
    )
  );
  ret = Rf_eval(e, R_GlobalEnv);

  if (TYPEOF(ret) == LGLSXP && LOGICAL(ret)[0]) {
      // If it\'s a logical vector and the first element is TRUE.
      result = true;
    } else {
      result = false;
    }
  
  UNPROTECT(1);
  return Rf_ScalarLogical(result);
'
)
checkver()