Example 4: id numbering

• Each scope has an array of identifers, each with the usual symbol table info

• Each array is indexed from 0

• In a context, use a stack of surrounding scopes

• The lookup algorithm is:

  • if index within bounds, look in first array
  • if not, subtract array size, pop array, repeat

• In addition, allow array entries of the form:

  • 3 = renumbering of outer 7

• This allows you eg to document free variables