Turnstyle – An esoteric, graphical functional language | Hacker News Reader

Turnstyle – An esoteric, graphical functional language

jaspervdj.be

141 pointsJNRowe8 comments

I'm a bit confused about what really is being interpreted here, because my reading of the specification indicates that the entire image is read as a single expression in the lambda calculus but the graphic interpreter looks like a procedural execution at the first glance. Is it just a visualization of beta-reduction in progress?

EDIT: I think I got it and I think calling this as an "encoding" is a misnomer. The program starts with a single term `turnstyle(x, y, dir)` which gets lazily evaluated to the actual term. So not only the evaluation might be lazy, but the parsing is also lazy and this is a key point of this esolang which should be highlighted more in my opinion.

This seems cool, but I’m having difficulty understanding the specification. It would be nice if there were some examples of e.g. 2+3 , (lambda f. lambda x. (f (f x)))(lambda y. (y+2)) 3 ?

`2 + 3` would be internally `((prim(3, 1) 2) 3)`, which can be composed of following fragments (where `^>v<` indicates the direction and the position of the current turnstile):

                        AA
    prim(3, 1):         >BBB
                        C

    literal 2:          AvB
                         CC

    literal 3:          AvB
                        CCC

                        A
    (prim(3,1) 2):      >*****prim(3,1)
                        *
                        *
                        2

                        A
    ((prim(3,1) 2) 3):  >*****(prim(3,1) 2)
                        *
                        *
                        3

So assuming that each distinct letter corresponds to a distinct color, one possible encoding would be:

     A    A    BB
    >>BBBBBCCCCCD
     B    C    AD
     B    C     D
    CBD  DCA
    AAA   BB

The specification allows for a simple "identity" pattern which can be used to extend otherwise overlapping patterns here. The following, if I did everything right, would be more compact but much harder to decipher:

    CADABB
    >>BBCD
    CBDCAD
    AAABBD

Is it similar to https://github.com/mxgmn/MarkovJunior

While both MJ and Turnstyle are Turing-complete, Turnstyle shares more similarities with Piet (mentioned by the author), Wireworld, and, of course, Conway's Game of Life.

I didn't understand the language but the examples look amazing. Are there any others like that?

Edit: Another one is Cellpond https://cellpond.cool/ https://github.com/TodePond/CellPond

Worth maybe calling out that there is a few academic language implementations using this name (turnstile, turnstile+) https://docs.racket-lang.org/turnstile. It's not a standalone language but worth pointing out

This is an esolang and that's an academic language. I'm pretty sure neither one cares to optimize for searchability.

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