s0rg/grid

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# grid

Generic 2D grid

# features

- [DDA RayCasting](https://lodev.org/cgtutor/raycasting.html)
- [A-Star pathfinding](https://en.wikipedia.org/wiki/A*_search_algorithm)
- [Ray-based line of sight](https://en.wikipedia.org/wiki/Line_of_sight_(video_games))
- [Recursive ShadowCasting](http://www.roguebasin.com/index.php/Shadow_casting)
- [Dijkstra maps](http://www.roguebasin.com/index.php/Dijkstra_Maps_Visualized)
- [Bresenham's lines](https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm)
- 100% test cover

# usage

```go
import (
    "image"

    "github.com/s0rg/grid"
)

const mapW, mapH = 100, 100

func valueExample() {
    // working with value-types is straightforward
    g := grid.New[int](image.Rect(0, 0, mapW, mapH))

    // now grid is filled with nil-value for your type
    // you still can re-fill it with some other values:
    g.Fill(func() int {
        return 1
    })
}

func pointerExample() {
    // working with pointer-types is same, but you now you must to pre-fill them
    type mycell struct {}

    g := grid.New[*mycell](image.Rect(0, 0, mapW, mapH))

    // now grid is filled with nil's, so you need pre-fill it with some values,
    // otherwise you will access those nil's with Get / MustGet methods.
    g.Fill(func() *mycell {
        return &mycell{}
    })
}

func usageExample() {
    type mycell struct {
        wall bool
    }

    g := grid.New[*mycell](image.Rect(0, 0, mapW, mapH))

    g.Fill(func() *mycell {
        return &mycell{}
    })

    pt := image.Pt(10, 10)

    // set new value
    g.Set(pt, &mycell{wall: true})

    // update existing value
    if v, ok := g.Get(pt); ok {
        v.wall = false
    }

    // shorthand, for above, will panic on out-of-bounds access
    g.MustGet(pt).wall = true

    // iterate items
    g.Iter(func(p image.Point, c *mycell) (next bool) {
        if c.wall {
            // wall found
        }

        return true
    })
}
```

# example

[Here](https://github.com/s0rg/grid/blob/master/_example/main.go) is a full example.

You can run it with `go run _example/main.go` to see results.

# benchmarks

run:

```bash
make bench
```

results:

```
goos: linux
goarch: amd64
pkg: github.com/s0rg/grid
cpu: AMD Ryzen 5 5500U with Radeon Graphics
BenchmarkGrid/Set-12             1000000000            0.8108 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/Get-12             641611768            1.764 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/Neighbours-12      52243890           23.41 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/LineBresenham-12             4416172          269.0 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/CastRay-12                   3829839          321.1 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/CastShadow-12                  32648        36950 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/LineOfSight-12                  9897       114576 ns/op          0 B/op          0 allocs/op
BenchmarkGrid/DijkstraMap-12                  1029      1190195 ns/op      20656 B/op          3 allocs/op
BenchmarkGrid/Path-12                          372      3225325 ns/op     997588 B/op      13643 allocs/op
PASS
ok      github.com/s0rg/grid    12.098s
```