So “why” exactly do we study deterministic and non-deterministic finite automata (DFA/NFAs)?

In this article we further develop Piponi’s approach, which employs a number of beautiful algorithmic techniques from the world of functional programming, to build a Java library for incremental regular expression matching. This is also an interesting investigation into how the functional approach blends together with an imperative language.

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“Incremental” means “match result is efficiently maintained under certain operations”, where the operations include concatenating two strings and splitting a string in part around an index. Obviously, these two operations form a basis for all kinds of rearrangements, such as inserting or deleting a word from the middle of a string, or appending characters to its back or front, etc.