# Overview

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## About

Library polyclip-go is a pure Go, MIT-licensed implementation of an algorithm for Boolean operations on 2D polygons (invented by F. MartÃnez, A.J. Rueda, F.R. Feito) -- that is, for calculation of polygon intersection, union, difference and xor.

The original paper describes the algorithm as performing in time *O((n+k) log n)*, where *n* is number of all edges of all polygons in operation, and *k* is number of intersections of all polygon edges.

## Example

Simplest Go program using polyclip-go for calculating intersection of a square and triangle:

// example.go package main import ( "fmt" "github.com/akavel/polyclip-go" // or: bitbucket.org/... ) func main() { subject := polyclip.Polygon{{{1, 1}, {1, 2}, {2, 2}, {2, 1}}} // small square clipping := polyclip.Polygon{{{0, 0}, {0, 3}, {3, 0}}} // overlapping triangle result := subject.Construct(polyclip.INTERSECTION, clipping) // will print triangle: [[{1 1} {1 2} {2 1}]] fmt.Println(result) }

To compile and run the program above, execute the usual sequence of commands:

go get github.com/akavel/polyclip-go # or: bitbucket.org/... go build example.go ./example # Windows: example.exe

Note:the polyclip-go library is developed for a fairly modern (at the time of writing) version of Go compiler, known as Go 1 RC1. If you have an older "release" version of Go, you may have problems compiling, and you are advised to switch to a newer "weekly" version. On the other hand, if you do have a newer version and encounter problems, please try using the`go fix`

tool to update the polyclip-go library. I'll also be grateful if you could contact me about that.

For full package documentation, run locally `godoc github.com/akavel/polyclip-go`

, or visit online documentation for polyclip-go.

## See also

- Online godoc for polyclip-go (courtesy of http://gopkgdoc.appspot.com).
- Microsite about the original algorithm, from its authors (with PDF, and public-domain code in C++).
- The as3polyclip library -- a MIT-licensed ActionScript3 library implementing this same algorithm (it actually served as a base for polyclip-go). The page also contains some thoughts with regards to speed of the algorithm.