Top-Down AST Construction of Regular Expressions with Recursive Descent

In my past projects when needed I have always implemented AST building parsers for regular expressions bottom-up by using the shunting yard algorithm. I've covered the process of doing so in my post on Thompsons Construction. While this approach certai

Balanced Deletion for in-memory B+ Trees

When it comes to data structures - especially self balancing data structures - it is no secret that the algorithms for removing an entry are often many, many times more complex than the algorithms for adding a value. Anyone w

Building an AST from a Regular Expression Bottom-up

This post was originally featured as a section of my post on implementing Thompsons Construction for NFA from a regular expression. Having since implemented several FA constructions, all of which utilized an AST representation of the given exp

The Aho, Sethi, Ullman Direct DFA Construction Part 2: Building the DFA from the Followpos Table

In part one of this post I covered building and annotating an abstract syntax tree from a postfix regular expression, as well as populating the firstpos, lastpos, and followpos sets for each node in the AST is it relates to it's position in the regular

The Aho, Sethi, Ullman Direct DFA Construction, Part 1: Constructing the Followpos Table

Todays post is an overview of a implementing the Aho-Sethi-Ullman Direct DFA Construction algorithm, aka "Algorithm 3.5: Construction of a DFA from a Regular Expression" as originally found in "the dragon" book[1]. This post is going to go deep in the

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