vi-turing - vi is Turing complete!

vi-turing is a Turing Machine interpreter written in form of vi keyboard macros. This proves that - given enough scratch space - vi macros are Turing complete!

Usage

• Open vi-turing.vi in your favorite vi (ex-vi, nvi, elvis, vim are currently supported).
• Load vi-turing.vi's macros: ESC :source % RETURN
• Initialize: \I
• Run: \\

Lessons learned

The following quirks of different vi versions were encountered during development of this:

• In ex-vi, you cannot yank from within a nontrivial macro. Example: :map \a yl, :map \\ \ap -> beep, "p" will not paste anything.
• In ex-vi, you cannot paste from any register other than the default one from within a macro. Example: :map \\ "ayl"ap -> "Can't put partial line inside macro".
• In elvis, @@ only executes unnamed registers. "ayl@@ does not work there.
• In ex-vi, you cannot use marks from within a nontrivial macro.
• vi implementations do not agree on where the cursor is put after pasting from a register.
  • ex-vi: last character of the paste.
  • nvi: first character of the paste.
  • elvis: last character of the paste.
  • vim: last character of the paste.