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.\" ========================================================================
.\"
.IX Title "Math::ConvexHull::MonotoneChain 3pm"
.TH Math::ConvexHull::MonotoneChain 3pm "2011-11-09" "perl v5.20.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Math::ConvexHull::MonotoneChain \- Andrew's monotone chain algorithm for finding a convex hull in 2D
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 10
\&  use Math::ConvexHull::MonotoneChain \*(Aqconvex_hull\*(Aq;
\&  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], ]
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is somewhat experimental still.
.PP
This (\s-1XS\s0) module optionally exports a single function \f(CW\*(C`convex_hull\*(C'\fR
which calculates the convex hull of the input points and returns it.
The algorithm is \f(CW\*(C`O(n log n)\*(C'\fR due to having to sort the input list,
but should be somewhat faster than a plain Graham's scan (also \f(CW\*(C`O(n log n)\*(C'\fR)
in practice since it avoids polar coordinates.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "convex_hull"
.IX Subsection "convex_hull"
Expects an array ref of points as input, returns an array ref of 
of the points in the convex hull, ordered counter-clockwise.
.PP
\&\fIpoint\fR refers to an array reference containing an X, and a Y coordinate.
.PP
For less than three input points, this will return an array reference
whose elements are the input points (without cloning).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Math::ConvexHull, which uses Graham's scan in pure Perl.
.SH "AUTHOR"
.IX Header "AUTHOR"
Steffen Mueller, <smueller@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (C) 2011 by Steffen Mueller
.PP
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.