Multidimensional Arrays

[Roger Browne]

I'm having some trouble accessing elements of multidimensional arrays
from PIR, and I'm not sure if what I want to do is buggy or
unimplemented, or if I'm simply doing it the wrong way.

I have no problem accessing a one-dimensional Array with either an
integer index, or with a PMC index of type Integer:

   .sub "main" :main

      # Set up an array ["zero", "one"]
      .local pmc array
      array = new .Array
      array = 2
      array[0] = "zero"
      array[1] = "one"

      # print the final element (prints "one" as expected)
      $S0 = array[1]
      print $S0
      print "\n"

      # print the final element another way (prints "one" as expected)
      $P0 = new .Integer
      $P0 = 1
      $S0 = array[$P0]
      print $S0
      print "\n"

   .end

But if I try the same thing with an Array of Arrays, I can use literal
integers for the Array offsets, but not Integer PMCs:

   .sub "main" :main

      # Set up an array of arrays [["zero", "one"], ["two", "three"]]
      .local pmc array, subarray1, subarray2
      subarray1 = new .Array
      subarray1 = 2
      subarray1[0] = "zero"
      subarray1[1] = "one"

      subarray2 = new .Array
      subarray2 = 2
      subarray2[0] = "two"
      subarray2[1] = "three"

      array = new .Array
      array = 2
      array[0] = subarray1
      array[1] = subarray2

      # print the final element (prints "three" as expected)
      $S0 = array[1; 1]
      print $S0
      print "\n"

      # print the final element another way
      $P0 = new .Integer
      $P0 = 1
      $P1 = new .Integer
      $P1 = 1
      $S0 = array[$P0; $P1]  # [1]
      print $S0
      print "\n"

   .end

The above code aborts with "build_key: wrong register set" at [1].

Can I use multi-dimensional PMC keys from PIR? There are opcodes like
"new_key" and "set_key" in pdd06, but they don't appear to be
implemented.

Or should I be building the key myself by using the ".Key" PMC?

Regards,
Roger Browne