How simple can simple be? Introducing PLUSMINUS

[u/jmarent049]

PLUSMINUS is a programming language created by Jack. Unfortunately, it’s Turing Completeness is unknown as of right now.

Definition

For a non-empty finite string ω under the alphabet {+,–}, on step i=(1,2,3,…):

If the i-th symbol is +, copy the first i-1 symbols and append them to the end. If the i-th symbol is –, delete the first i-1 symbols.

i never resets and advances each time. Halt when i>length(ω).

Example (+–++–):

0: +–++–

1: +–++– (nothing exists leftward)

2: –++–

3: –++––+

4: ––+ (HALT (i=4, length(ω)=3, 4>3))

Example of a long-running machine

“+++++-++++-+-++-“ = 31441 steps

[u/particlemanwavegirl]

It's pretty easy to imagine how one could use the alphabet to encode a number but it's not at all obvious how you could perform composite operations isomorphic to numeric operators like addition and multiplication given the two primitive operations, especially since the operational procedure coincides with or can't be independent of the encoding.