While loop doing cell evaluation not completing

Question

I am trying to get a loop structure using While to repeatedly evaluate another cell referred to in its body (using a cell tag).

"this is the while construct";
x = 2;
y = 5;
While[x < y,
  NotebookLocate["code"];
  FrontEndTokenExecute["EvaluateCells"];
  x
  y
]

and this is the cell called "code"

"this cell contains the code i want to run";
x = x + 0.1;
y = y - 0.1;

My code seems to enter an endless loop.

What I expected was when the two numbers, x and y, became equal, the loop would stop. What am I doing wrong?

Answer 1

Here is an example for now. Notice that in the process[] function, if you intend to modify the input arguments, you have to make a temporary copy of them, since default passing in Mathematica is by value.

(*---- This function is the main driver ---*)
main[] := Module[{x = 2, y = 5},
   While[x < y,
    {x, y} = process[x, y];
    Print["x=", x, "y=", y];
    ]
   ];

(*---- my processing function called from a loop from somewhere *)
process[x0_, y0_] := 
 Module[{x = x0, y = y0},(*to allow us to modify input*)
  (*assume we are using x and y much more here *)

  x = x + 0.1;
  y = y - 0.1;

  (*we are done, let return the result*)
  {x, y}
  ]

Answer 2

Try this:

x = 2;
y = 5;

Monitor[
 While[x < y,
  NotebookEvaluate["code.nb"]
  ],
 {x, y}
 ]

Monitor is optional. I used it to make sure that something was happening. :)