* Formidicae byte code

Formidicae assembly code is assembled into byte code by the Formidicae
assembler.  Formidicae byte code is a sequence of words.  Each word
contains sixteen bits in bigendian byte order.  States consist of two 
or more words.  The first word contains the state operator and all 
operands; the remaining words contain the continuation states.  A
continuation state word specifies the index of the next state that should 
be followed after the success or failure of an operation.


There are two types of operators; simple and conditional.  A simple
operator (turn, drop, mark, and unmark) will always succeed, and thus 
is always followed by only one continuation word.  Conditional 
operations (sense, flip, move, pick-up) may fail for various reasons, and
are thus followed by a second continuation word to specify the destination
of a failed operation.

Currently, the most words in a single state may be three, with the 
given ant instruction set.

The four high-order bits in a state operation word contain the opcode.
The remaining bits contain the operands to the operator.

SENSE   0000__ddmiiiaaaa
  dd represents the direction -- 00 is HERE, 01 is AHEAD, 10 is LEFT, &
  11 is RIGHT --; m tells whether this is testing for a pheromone; iii
  is the pheromone index if m is set; aaaaaa describe the attribute if
  m is not set.  The remaining two bits are ignored/reserved.  The
  following attributes are defined:
    0000 - friend?
    0001 - foe?
    0010 - friend-with-food?
    0011 - foe-with-food?
    0100 - home?
    0101 - foe-home?
    0110 - foe-mark?
    0111 - food?
    1000 - rock?
    1001 - water?
  Following are two state index words.

TURN    0001d___________
  d represents the direction; 0 is LEFT & 1 is RIGHT.  Following is one
  state index word.

MOVE    0010____________
PICK-UP 0011____________
  No operands.  Following are two state index words.

DROP    0100____________
  No operands.  Following is one state index word.

MARK    0101aaaaaaaaaiii
UNMARK  0110_________iii
  iii is the index of the pheromone flag, aaa is the amount of pheromone. 
  Following is one state index word.

FLIP    0111pppppppppppp
  [0,pppppppppppp) is the range of the random number to generate to
  determine which state to jump to.

* Filename conventions

  .ant  - Formicidae code
  .anto - separately compiled Formicidae code
  .anta - assembly code generated by linking .anto files, equivalent in
          format to .anto files, except that there are no unresolved
          state indices as continuations
  .antc - assembled Formicidae code, suitable for simulating