um.cr

class Um
  def initialize(program, key = "")
    @array = [] of Array
    @register = [0_u32] * 8
    @finger = 0_u32

    @a = @b = @c = @z = @value = 0_u32

    @array << program
  end

  def spin(stopchar = nil)
    loop do
      platter = @array[0][@finger] as UInt32
      opcode = (platter >> 28) & 0xF

      case opcode
      when  2; array_amendment
      end
    end
  end

  def array_amendment
    # $a[$b] = $c
    a = @register[@a]
    b = @register[@b]
    c = @register[@c]
    # Array is an array of arrays of UInt32
    # puts @array[a].class   #=> Array(UInt32)
    # puts @array[a][b]class #=> UInt32
    # puts c.class           #=> UInt32
    @array[a][b] = c
    # in ./crystal/um.cr:32: no overload matches 'Array(Fiber)#[]=' with types UInt32, UInt32
    # Overloads are:
    #  - Array(Fiber)#[]=(index : Int, value : Fiber)
  end
end

program = [0_u32]
Um.new(program).spin