# bitbucket.org/akavel/polyclip-go

About
—–
Library polyclip-go is a pure Go, MIT-licensed implementation of an algorithm for Boolean operations on 2D polygons (invented by F. Martínez, 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.