virtual turing machine - readme
the old version : vtm
Some years ago I wrote a "vtm" command line tool
in perl. It's installed on csmarlboro.org among
other places, and runs *.vtm files as described at
the new spec : yvtm
This year I'm updating that idea with a YML Virtual Turing Machine (yvtm) spec.
# busybeaver3.yvtm
tape: "0"
start: one
blank: "0"
accept: []
reject: []
machine:
# current read next write move
# state symbol state symbol to
# ----- ------ -------- ----- -----
- [ one, 0, two, 1, right ]
- [ one, 1, HALT, 1, right ]
- [ two, 0, three, 0, right ]
- [ two, 1, two, 1, right ]
- [ three, 0, three, 1, left ]
- [ three, 1, one, 1, left ]
To read this into a python program, for example, all you need do is
import yaml
turing = yaml.load(open('busybeaver3.yvtm'))
which would give you this data structure
turing = {'tape' : '0',
'accept' : [],
'reject' : [],
'blank' : '0',
'machine': [['one', 0, 'two', 1, 'right'],
['one', 1, 'HALT', 1, 'right'],
['two', 0, 'three', 0, 'right'],
['two', 1, 'two', 1, 'right'],
['three', 0, 'three', 1, 'left'],
['three', 1, 'one', 1, 'left']]
}
(Note: YAML will put bare words into quote strings. However, it will also
convert bare numbers into number by default, so you will need to
be a bit careful with symbols like 0 and convert them appropriately.)
I've also written a yvtm.py program which gives output like this :
$ python yvtm.py -help
yvtm.py : YAML Virtual Turing Machine in python
Usage: python yvtm.py [-quiet] [-help] [-tape=...] filename.yvtm
$ python yvtm.py -quiet busybeaver3.yvtm
1 1 1 <1> 1 1 : HALT
$ python yvtm.py busybeaver3.yvtm
<0> : one
1 <0> : two
1 0 <0> : three
1 <0> 1 : three
<1> 1 1 : three
<0> 1 1 1 : one
1 <1> 1 1 : two
1 1 <1> 1 : two
1 1 1 <1> : two
1 1 1 1 <0> : two
1 1 1 1 0 <0> : three
1 1 1 1 <0> 1 : three
1 1 1 <1> 1 1 : three
1 1 <1> 1 1 1 : one
1 1 1 <1> 1 1 : HALT
** HALT ** (No matching rule)
After giving you a chance to write something that
implements this, I'll upload mine.
