Null values in arrays

Context

As mentioned in this previous post, array implementation induces a limitation: elements cannot be null. Let's now see how to deal with zeros.
To access an element in an array, we need to go through all elements, so use a loop. And loops stop when value reached is null. Therefore, our current array structure doesn't fit.

However, it's still possible to have arrays with 2 memory cells per element: first that contains a non-zero value (any value, but let's say 1), and second that contains the actual element value.
Then, to access elements in the array, we need to iterate on blocks of 2 cells.

Code sample

>>+ first separator

>>, read char

[

  >++++[-<----------->]+< comma check

  [---- convert to digit value

    >++++++++[-<<[->+>>+<<<]>>>[-<<<+>>>]<]<[-<+>] multiply current by ten and add new digit

  ]>[ comma case

    <+>->> add cell with 1 and start next number

  ]<,]

<<[<<]>> go back to array last element (first cell) then back to the array beginning

This block of code read comma-separated decimal numbers, including 0, and store them in memory cells separated by cells containing 1.

The last line shows how to move back to the array first element.