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;; Universal Turing Machine Simulation
;; A wax feature demo
​
; enums for shift directions
(@define STAY  0)
(@define LEFT  1)
(@define RIGHT 2)
​
; datastructure for the transition function
(struct transition
    (let q_curr int) ; current state
    (let q_targ int) ; target state
    (let sym_r  int) ; read symbol
    (let sym_w  int) ; write symbol
    (let shift  int) ; shift direction
)
​
; datastructure for the turing machine
; (map int int) is used to represent the tape,
; mapping position to symbol, to simulate "infinite" length.
; tmin/tmax are tape extremas for visualization
(struct machine
    (let state int) ; current state
    (let head  int)
    (let tape  (map int int))
    (let tmin  int) ; leftmost  visited tape position
    (let tmax  int) ; rightmost visited tape position
)
​
; simulate the turing machine for 1 step.
(func step
    (param M (struct machine))
    (param D (arr (struct transition)))
    (let tape (map int int) (get M tape))
​
    ; check each transition function, to see if conditions apply
    (for i 0 (< i (# D)) 1 (do
​
        (if (&&
            (= (get M state)           (get D i q_curr))
            (= (get tape (get M head)) (get D i sym_r ))
        ) (then
            ; execute the transition
            (set tape  (get M head) (get D i sym_w ))
            (set M state            (get D i q_targ))
            (if (= (get D i shift) @LEFT) (then
                (set M head (- (get M head) 1))
            )(else(if (= (get D i shift) @RIGHT) (then
                (set M head (+ (get M head) 1))
            ))))
            (break)

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/*****************************************
 * turing                                *
 *****************************************/
/* Compiled by WAXC (Version Mar  2 2021)*/
​
​
module turing{
/*=== WAX Standard Library BEGIN ===*/
const w_slice=(x:Array<any>|string,i:number,n:number)=>x.slice(i,i+n);
/*=== WAX Standard Library END   ===*/
​
/*=== User Code            BEGIN ===*/
​
  export class transition{
    q_curr:number=0;
    q_targ:number=0;
    sym_r:number=0;
    sym_w:number=0;
    shift:number=0;
  };
  export class machine{
    state:number=0;
    head:number=0;
    tape:Record<number,number>=(null as any);
    tmin:number=0;
    tmax:number=0;
  };
  export function step(M:machine,D:Array<transition>){
    let tape:Record<number,number>=(null as any);
    tape=((M).tape);
    for(let i:number=(0);Number((i)<(D.length));i+=(1)){
      if(((Number((((M).state))==(((((D)[i])).q_curr))))&&(Number((((tape)[((M).head)]??0))==(((((D)[i])).sym_r)))))){
        ((tape)[((M).head)]=((((D)[i])).sym_w));
        ((M).state=((((D)[i])).q_targ));
        if(Number((((((D)[i])).shift))==(1))){
          ((M).head=((((M).head))-(1)));
        }else{
          if(Number((((((D)[i])).shift))==(2))){
            ((M).head=((((M).head))+(1)));
          };
        };
        break;
      };
    };
    if(Number((((M).head))<(((M).tmin)))){
      ((M).tmin=((M).head));
    };
    if(Number((((M).head))>(((M).tmax)))){
      ((M).tmax=((M).head));
    };
  };