What's the difference between the ruby irb prompt modes?

Question

I can change the irb prompt mode with

irb --prompt prompt-mode

I can see what null and simple does, but I can't tell the difference between null and xmp and the difference between default/classic/inf-ruby. Can someone explain to me what these other modes do? It seems pointless to have multiple modes doing the same thing.

Answer 1

Once you read the article cldwalker posted above, you may want to design a custom prompt, here's mine for example:

IRB.conf[:PROMPT][:CUSTOM] = {
  :PROMPT_I => ">> ",
  :PROMPT_S => "%l>> ",
  :PROMPT_C => ".. ",
  :PROMPT_N => ".. ",
  :RETURN => "=> %s\n"
}
IRB.conf[:PROMPT_MODE] = :CUSTOM
IRB.conf[:AUTO_INDENT] = true