Lua: Search key in table, increment index if not and retry - checkbox

Question

Situation:
table = { this, that, something else, x_coord, y_coord }
table.x_coord = { 1,2,3,4,7,8,n}
table.y_coord = { 2,4,5,9,n} -- numbers aren't fix
table.check_boxes = { [12] = a function,
[14] = a function,
[15] = a function,
[24] = a function,
[29] = a function,
....(n) }
As you can see, the x/y_coords forming check_boxes. For example:
table.x_coord[1]..table.y_coord[1] ~ table.check_boxes[1]
I use this to move the cursor in the Terminal between the check_boxes.
The problem now is in my cursormovement.
Currently I got a function that's searching for the next x/y_coord to the left/right/up/down depending on the given input (arrow-keys).
With return/space I call the function behind the checkbox.
Now, that could set the Cursor on positions where no check_boxes are given. Actually that's not a big deal, because when input == space/return, an inputhandler calls the function at
table.check_boxes[table.x_coorx[x_index]..table.y_coords[y_index]]
So if the cursor doesn't point on a function, just nothing happens.
But now I want the cursor to be forced to the next check_box. What can I do?
My Idea so far:
following function either for x or y, depending on input left/right up/down:
while true do
for k, v in pairs(table.check_boxes) do
if(table.x_coord[x_index] .. table.y_coord[y_index] == k then break end
end -- break -> okay, coord is at a checkbox
x_index = x_index + 1 -- or -1
if table.x_coord[x_index] == nil then
x_index = 1
end
end
The Problem now is that the last if will not allow cases like x_coord = {1,3} because it will set x_index to 1 if 2 is reached.
Any tips?
Edit:
Now I got that one going:
function cursorTioNextBoxRight()
searc_index = x_index
search = true
while search do
search_index = search_index + 1
if search_index > #table.x_coord then
search_index = 1
end
for k, v in pairs(table.check_boxes) do
if tonumber(table.x_coord[search_index..table.y_coord[y_index] == k then
x_index = search_index -- YAAAY
search = false
break
end
end
end
I'ts damn slow.

Answer 1

local x_newIndex = x_index + 1 --[[ or -1 --]]
x_index = table.x_coord[x_newIndex] and x_newIndex or x_index
x_index becomes x_newIndex when x_newIndex exists in the table otherwise it stays the old x_index

Answer 2

function cursorTioNextBoxRight()
searc_index = x_index
search = true
while search do
search_index = search_index + 1
if search_index > #table.x_coord then
search_index = 1
end
for k, v in pairs(table.check_boxes) do
if tonumber(table.x_coord[search_index..table.y_coord[y_index] == k then
x_index = search_index -- YAAAY
search = false
break
end
end
end