diff.mq

Text and array diffing utilities implemented as an mq module, built on top of mq's native Myers-diff engine — the same one that powers assert_eq's failure output.

Features

• Line, word, character, and generic array diffing
• added / removed / unchanged / has_changes / stat helpers to inspect a diff result
• Renders a diff as unified-diff-style text or a fenced ```diff Markdown code block, ready to drop into a changelog or PR description
• No hand-rolled LCS implementation — delegates to mq's native diff builtin for correctness and speed

Installation

Copy diff.mq to your mq module directory, or place it anywhere and reference it with -L.

cp diff.mq ~/.local/mq/config/

HTTP Import (no local installation needed)

If mq was built with the http-import feature, you can import directly from GitHub without any local setup:

mq -I raw 'import "github.com/harehare/diff.mq" | diff::diff_lines(read_file("old.md"), read_file("new.md"))'

Pin to a specific release with @vX.Y.Z:

mq -I raw 'import "github.com/harehare/diff.mq@v0.1.0" | ...'

Usage

mq -L /path/to/modules -I raw \
  'import "diff" | diff::diff_lines(read_file("old.md"), read_file("new.md"))'

If you copied it to the mq built-in module directory:

mq -I raw 'import "diff" | ...'

API

Computing a diff

Function	Description
diff_lines(a, b)	Diffs two strings line by line
diff_words(a, b)	Diffs two strings word by word (whitespace-separated)
diff_chars(a, b)	Diffs two strings character by character
diff_array(a, b)	Diffs two arbitrary arrays of values (numbers, dicts, Markdown nodes, …)

Each returns an array of {tag, value} entries, where tag is one of "equal", "insert", "delete". Adjacent delete/insert pairs of strings also carry an inline field with a character-level sub-diff, useful for building your own word-level renderers.

Inspecting a diff result

Function	Description
is_equal(entry) / is_added(entry) / is_removed(entry)	Predicates on a single entry
added(result) / removed(result) / unchanged(result)	Extract just the values with that tag
has_changes(result)	true if the result contains any insert/delete
stat(result)	{added, removed, unchanged} counts

Rendering

Function	Description
to_unified(result)	Renders as unified-diff-style text (+ , - , prefixed lines)
to_markdown(result)	Wraps to_unified output in a fenced ```diff code block

Example

mq -L . -I raw \
  'import "diff" | diff::to_markdown(diff::diff_lines("a\nb\nc", "a\nx\nc"))' <<< "x"

  a
- b
+ x
  c

Check whether two revisions of a document changed at all, and by how much:

import "diff"
| let r = diff::diff_lines(old_text, new_text)
| if (diff::has_changes(r)): diff::stat(r) else: "no changes" end

Compatibility

Requires mq v0.6 or later (uses the native _diff builtin).

License

MIT