Math::...neChain(3pm)

💖 NAME 💖

okay bestie, gather round, because this one is literally Math::ConvexHull::MonotoneChain — it's Andrew's monotone chain algorithm for finding a convex hull in 2D ✨

(and yeah, this page lives in the User Contributed Perl Documentation manual, so you know it's a classic 🫶)

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🦋 SYNOPSIS 🦋

the whole vibe in one go:

  use Math::ConvexHull::MonotoneChain 'convex_hull';
  my $ch = convex_hull(
    [
      [0, 0],
      [0, 1],
      [1, 0],
      [0.5, 0.5],
      [1, 1],
    ]
  );

  # $ch is now:
  # [ [0, 0],
  #   [1, 0],
  #   [1, 1],
  #   [0, 1], ]

look at it go 🌸

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✨ DESCRIPTION ✨

full transparency, bestie: this is somewhat experimental still. 🙈

this (XS) module optionally exports a single function, convex_hull, which calculates the convex hull of the input points and hands it right back to you. it's giving toolkit, it's giving main character 💅

the algorithm is O(n log n) because it has to sort the input list — no way around that, that's just the toll you pay to get in 🎀 — but it should be somewhat faster than a plain Graham's scan (which is also O(n log n)) in practice, since it avoids polar coordinates. obsessed with the efficiency honestly 🔥

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👑 FUNCTIONS 👑

🌈 convex_hull

expects an array ref of points as input, and returns an array ref of the points in the convex hull, ordered counter-clockwise ⭐

a point refers to an array reference containing an X, and a Y coordinate. that's it, that's the whole shape of it 🍓

heads up: for less than three input points, this will return an array reference whose elements are the input points (without cloning). so no sneaky copies, okay? 💀

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🧚 SEE ALSO 🧚

• Math::ConvexHull, which uses Graham's scan in pure Perl — its cousin, different outfit 💜

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💜 AUTHOR 💜

Steffen Mueller, <smueller@cpan.org> 🫶

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🎀 COPYRIGHT AND LICENSE 🎀

Copyright (C) 2011 by Steffen Mueller

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.0 or, at your option, any later version of Perl 5 you may have available. 📜

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and that's the whole page, bestie 💖 this was perl v5.42.3 documenting Math::...neChain(3pm), dated 2026-08-19 — slay, no cap, periodt ✨🌈👑