Regenerate: a language generator for extended regular expressions

Abstract

Regular expressions are part of every programmer’s toolbox. They are used for a wide variety of language-related tasks and there are many algorithms for manipulating them. In particular, matching algorithms that detect whether a word belongs to the language described by a regular expression are well explored, yet new algorithms appear frequently. However, there is no satisfactory methodology for testing such matchers. We propose a testing methodology which is based on generating positive as well as negative examples of words in the language. To this end, we present a new algorithm to generate the language described by a generalized regular expression with intersection and complement operators. The complement operator allows us to generate both positive and negative example words from a given regular expression. We implement our generator in Haskell and OCaml and show that its performance is more than adequate for testing.

Generalized Convolution and Efficient Language Recognition

“…Piponi and Yorgey [2015] investigated regular expressions and their relationship to the semiring of polynomial functors, as well as data type derivatives and dissections. Radanne and Thiemann [2018] explored regular expressions extended to include intersection and complement (as did Brzozowski) with an emphasis on testing. McIlroy [1999McIlroy [ , 2001 formulated power series as a small and beautiful collection of operations on infinite coefficient streams, including not only the arithmetic operations, but also inversion and composition, as well as differentiation and integration.…”