calling C function directly (a la julia)

ccall.R

ccall <- function(fun, ..., depends = character(), plugins = character(), verbose = FALSE ){ 
  dots <- list(...)    
  if( length(dots) ){
    code <- sprintf( '
    SEXP fun(%s){
      return wrap( %s( %s ) ) ;
    }',
    paste( sprintf( "SEXP arg%d", seq_along(dots)), collapse = ", " ),
    fun, 
    paste( sprintf( "Rcpp::internal::converter(arg%d)", seq_along(dots) ), collapse = ", " )
    )                      
    f <- cppFunction(code, depends = depends, plugins = plugins, verbose = verbose)
    do.call(f, dots)
  } else {
    evalCpp( sprintf( "%s()", fun ), depends = depends, plugins = plugins)    
  }
}

# example: 
ccall( "Rf_length", 1:10 )

This is just a convenience. It generates some code and compile it. Not quite what julia does. and see the wrap call, it is limited to what can be wraped