With this code you can convert regular expression given in the Python format to a (close) equivalent formal definition.
For a quick guide on Python regex, see the official documentation.
This is the formal definition we convert Python regex to:
a, b, c, ...
: members of the alphabet used in the expressionab
ora&b
: the concatenation ofa
andb
(i.e.,a
must be directly followed byb
)a|b
: the choice ofa
orb
(i.e., eithera
orb
is accepted); other literature also uses+
a*
: the Kleene Star operator (i.e.,a
can be repeated 0 or more times)
Hint: use
\e
for an empty string in inputs.
Run the script with
python main.py <destination> -e <expression>
where destination
must be one of REGEX
, SYA
, NFA
or DFA
.
REGEX
simply converts the given expression into a formal defintion regular expressionSYA
converts the given expression into a post-fix notation using the shunting-yard algorithmNFA
creates a nondeterministic finite automatonDFA
creates a deterministic finite automaton
Other optional arguments include -s
for strict mode. Here, an error is thrown instead of making any assumptions when converting an expression (e.g., for lookahead assertion).
Also, -d
enables debug mode, which prints conversion steps (i.e., all previous steps in the list above).
For a complete explanation of command-line arguments see
python main.py -h
python main.py REGEX -e '(ab|c)a*'
(a&b|c)&a*
python main.py SYA -e '(ab|c)a*'
ab&c|a*&
python main.py NFA -e '(ab|c)a*'
States
Q: {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
Initial State(s)
q0: 1
Final State(s)
F: [10]
Transition Function
δ:
1 -> 2 with '##e##'
1 -> 5 with '##e##'
4 -> 7 with '##e##'
6 -> 7 with '##e##'
2 -> 3 with 'a'
3 -> 4 with 'b'
5 -> 6 with 'c'
7 -> 8 with '##e##'
7 -> 10 with '##e##'
9 -> 10 with '##e##'
9 -> 8 with '##e##'
8 -> 9 with 'a'
python main.py DFA -e '(ab|c)a*'
States
Q: {1, 2, 3, 4, 5}
Initial State(s)
q0: 1
Final State(s)
F: [2, 4, 5]
Transition Function
δ:
1 -> 2 with 'c'
1 -> 3 with 'a'
3 -> 4 with 'b'
4 -> 5 with 'a'
5 -> 5 with 'a'
2 -> 5 with 'a'
python main.py SYA -e '(ab|c)a*' -d
Escaped string: (ab|c)a*
Operator-filled string: (a&b|c)&a*
Shunting-yard string: ab&c|a*&
ab&c|a*&
MIT License
Copyright (c) 2022 Tobias Kalmbach
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