trstools.py

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File        : README.md
Maintainer  : Felix C. Stegerman <[email protected]>
Date        : 2016-05-18

Copyright   : Copyright (C) 2016  Felix C. Stegerman
Version     : v0.1.1

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Description

trstools.py - python (2+3) term rewriting tools

See trstools.py for the code (with examples).

Examples

$ ./trstools.py --rule "f(x,h(x)) -> f(x,x)"      \
                --rule "f(g(x),y) -> f(x,h(y))"   \
                --rule "g(h(x))   -> h(g(x)))"    \
                --normalforms "f(g(h(g(h(x)))),y)"
f(h(h(g(x))),h(y))
f(h(h(g(g(x)))),y)

$ cat > /tmp/rules
f(x,h(x)) -> f(x,x)
f(g(x),y) -> f(x,h(y))
g(h(x))   -> h(g(x)))
^D

$ ./trstools.py --rules-from=/tmp/rules --critical-pairs
[ f(x,h(h(g(x)))), f(g(x),g(x)) ]
[ f(h(g(x)),z), f(h(x),h(z)) ]

$ ./trstools.py --rules-from=/tmp/rules --tree "f(g(h(g(h(x)))),y)" \
                                        --mark-nf
f(g(h(g(h(x)))),y)
  --1-->  f(h(g(h(x))),h(y))
    --2-->  f(h(h(g(x))),h(y))  NF
  --2-->  f(h(g(g(h(x)))),y)
    --2-->  f(h(g(h(g(x)))),y)
      --2-->  f(h(h(g(g(x)))),y)  NF
  --2-->  f(g(h(h(g(x)))),y)
    --1-->  f(h(h(g(x))),h(y))  NF
    --2-->  f(h(g(h(g(x)))),y)
      --2-->  f(h(h(g(g(x)))),y)  NF

# open (temporary) graph
$ ./trstools.py --rules-from=/tmp/rules --graph "f(g(h(g(h(x)))),y)"

# save graph ...
$ ./trstools.py --rules-from=/tmp/rules --graph "f(g(h(g(h(x)))),y)" \
                --output /tmp/graph.png
# ... and open
$ xdg-open /tmp/graph.png

Requirements

• pyparsing
• graphviz (to generate graphs)

Installing the requirements (Debian & Ubuntu)

$ apt-get install graphviz
$ apt-get install python-pyparsing    # for python 2, or
$ apt-get install python3-pyparsing   # for python 3

TODO

• properly implement unify()!
• no double lines in graph?!
• improve, make more efficient?!
• pypi package?!
• ...

License

GPLv3+ [1].

References

[1] GNU General Public License, version 3 --- https://www.gnu.org/licenses/gpl-3.0.html

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