This is a library for parsing and operating on formal regular expressions. The repository is divided into three modules:

• regex: A library for tokenizing and parsing regular expressions.
• derivative: A program for computing regular expression derivatives.
• reverse: A program for computing the reverse of regular expressions.

• Install smlnj:

apt install smlnj

• Install libgmp-dev:

apt install libgmp-dev

• Install mlton:

  • Download a release from here

  • Un-tar the downloaded file

  • Enter the untar-ed folder and run make install

• Run make. This will create two binaries, bin/reverse and bin/derive

• Compute a first-order derivative

$ make
$ bin/derive -e "aa|b" -x a -n 1
# Output: a|b

• Reverse an expression

$ make
$ bin/reverse "a|b"
# Output: b|a

This project is no longer maintained. See my jare for a more formal regex implementation using Elm.

This implementation is based on Professor Timothy Ng's lecture notes. The utility file util/check.sml is borrowed from Professor Adam Shaw's CMSC 22100.