r/step0_repl.r

   1 source("readline.r")
   2
   3 READ <- function(str) {
   4     return(str)
   5 }
   6
   7 EVAL <- function(ast, env) {
   8     return(ast)
   9 }
  10
  11 PRINT <- function(exp) {
  12     return(exp)
  13 }
  14
  15 rep <- function(str) {
  16     return(PRINT(EVAL(READ(str), "")))
  17 }
  18
  19 repeat {
  20     line <- readline("user> ")
  21     if (is.null(line)) { cat("\n"); break }
  22     tryCatch({
  23         cat(rep(line),"\n", sep="")
  24     }, error=function(err) {
  25         cat("Error: ", err$message,"\n", sep="")
  26     })
  27 }