The code for this post, as well as the post itself, are on github. This post is part 2 of a 3 part series. Part 1: Parsing Part 2: Generate an NFA Part 3: Evaluate an NFA Converting the Parse Tree to an NFA In the last post, we transformed the flat string representation of a regular expression to the hierarchical parse tree form. In this post we’ll transform the parse tree to a state machine.

The code for this post, as well as the post itself, are on github. This post is part 1 of a 3 part series. Part 1: Parsing Part 2: Generate an NFA Part 3: Evaluate an NFA Until recently, regular expressions seemed magical to me. I never understood how you could determine if a string matched a given regular expression. Now I know! Here’s how I implemented a basic regular expression engine in under 200 lines of code.

After 4 days climbing long moderates in Tuolumne Meadows, Eben and I were stoked to get out of the park for the weekend and escape the crowds on some eastside alpine rock. After a few minutes of flipping through the guidebook, we settled on the North Arete on Bear Creek Spire. The granite prow of Bear Creek Spire rises to 13713’, roughly 1500’ above the scree at its base. The North Arete climbs the steep north ridge line through 10 pitches up to the summit.