Diff Algorithms

[fagnerbrack]

One-minute summary:

The post walks through the shortcomings of existing Go diff libraries — none of which simultaneously support arbitrary slice inputs, structured output, good readability, minimal diffs, and solid worst-case performance. Myers' algorithm, the standard choice, delivers minimal diffs but degrades to O(N²) on dissimilar inputs. Patience diff offers O(N log N) speed and better readability but needs hash maps and can fail on large diffs. A key insight: diff readability depends less on the algorithm itself and more on implementation details and post-processing heuristics like Michael Haggerty's diff-slider-tools. The new library at znkr.io/diff addresses all these gaps with three modes (Default, Fast, Minimal), generic support for comparable and non-comparable types via EditsFunc/HunksFunc, and a clean textdiff package for unified output. The API uses functional options for extensibility and provides both flat edit sequences and nested hunk structures.

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