vimmmex is an illustration that a turing machine can be built from copy/paste/search/replace style operations, informally showing the turing-completeness of regular vim commands. we limit ourselves to only the "normal" vim commands - that is, vim "ex" commands (those commands that begin with a colon) and vimscript are avoided, as these are already powerful, and showing their turing completeness is trivial. specifically, vimmmex implements a brainf@!# interperter with vanilla vi commands.
to use the interpreter, open the file vimmmex in vanilla vim. if possible, reduce the font size so that the entire file fits on the screen - this will make observing execution easier. press gg2yy@" to launch the interpreter. the default BF program calculates prime numbers, up to 100. the numbers will appear on the output line (below "_o:") as they are calculated. calculations are performed by copying and pasting characters while moving about the file through searches and cursor movement keys.
| Calculating prime numbers |
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| ... while tracking the cursor movement |
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the vimmmex_raw file contains (non-ascii) vim special characters, such as ^M and ^R. vimmmex provides a pure-ascii version of the interpreter, in which special characters are inserted by the execution process itself, but uses an (ideally forbidden) vim "ex" command (the first line) to perform the substitution. this may be more conducive for copying and pasting the contents of the file.
the only non-vi compatible requirement is that "whichwrap" is set to at least "b,s" - this is the default for vim, and is automatically configured when "nocompatible" is set. this requirement is only in place for aesthetics, as it allows breaking one long line into several smaller lines.
vimmmex is a proof-of-concept from Christopher Domas (@xoreaxeaxeax).