Regex Chess

Overview

This skill provides strategic guidance for implementing chess move generators using only regular expressions. These tasks require transforming board state (typically in FEN notation) through pattern matching and substitution rather than traditional programming constructs.

Core Approach

Phase 1: Understand the String Representation

Before writing any patterns, thoroughly understand the board representation:

1. Parse the FEN structure: FEN notation encodes rank 8 to rank 1 (top to bottom), with files a-h (left to right) within each rank
2. Map coordinates to string positions: Determine the exact character index for each square after expanding digit placeholders (e.g., "8" becomes "........")
3. Document the ordering: Create a clear mapping of how squares appear sequentially in the expanded string

Phase 2: Start Minimal - One Move Type First

Critical: Get a single move type working completely before adding complexity.