brzozowski

Library for constructing generalized regular expressions (and more, in the future).

Examples

We can construct a simple regex saying that santas has many ho's, that is one or more.

>>> santa = many "ho"
>>> "hohoho" ^- santa
^((ho)+|ε)$

Deriving santa with respect to three ho's, gives us a regex matching remaining possible strings that also match santa. Seeing that (ho)+ | ε is saying zero or more ho's, we can further reduce this to (ho)*. It is easy to see that this regex contains the empty string but the ? function will tell you nonetheless.

>>> "hohoho" ? santa
True

We can also demonstrate some strings that do not match.

>>> "hahaha" ^- santa
^∅$
>>> "hahaha" ? santa
False
>>> -- santa does not laugh
>>> "" ^- santa
^(ho)+$
>>> "" ? santa
False
>>> -- santa needs at least one ho