/repl

Primary LanguageR

An R implementation of the top level REPL

Originally put together in 2008 to find out if all the pieces needed to build a full REPL at the R revel are available.

The public interface is

  • repl() for running a read-eval-print loop
  • quit() for exiting the repl.

I believe most major features available in 2008 are at least approximately supported, except for

  • catching a Q in a browser;
  • top level callbacks.

Q could be handled either by adding an appropriate restart in repl() and modifying the C internals of browser, or, better in the long run, by also writing the browser code in R and modifying do_browser to use the R version. Some fiddling with context entries is needed for that and to make sure that efficiency of return() calls isn't messed up. (With most code now being byte compiled this is less of an issue.)

Some minor issues:

  • return(1) at repl top level does not give an error and probably should.

  • In gui's the gui may think it is busy and so show the hour glass (Rgui)/spinner(AQUA). The spinner in AQUA seems to go away after a while.

  • Need to set up for i18n/L10n

  • Prompts should be determined by options settings and startup flags -- for now a fixed pair of prompts is used.

  • readline/input editing isn't quite right on at least some platforms (tty in particular). On AQUA do_addhistory doesn't seem to do anything.

Color support in xterm was provided by Deepayan Sarkar. This should probably be made configurable in some way.