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# quadtile-index
Convert between x,y map tile coordinates and a bitwise-interleaved single integer

Quadtiles use a 2-bit tile interleaved addresses. An **x** and **y** coordinate value bit representation of up to 26 bits each can be converted to a single integer value up to 56 bits. The limit is due to JavaScript's maximum lossless integer representation. For example, two 8 bit values **xxxx xxxx** and **yyyy yyyy** would produce a singel **xyxyxyxy xyxyxyxy xyxyxyxy xyxyxyxy** index value.

The library will assert the validity of each value, and allows optional zoom for additional verification.

For more info, see [quadtile indexes info](https://wiki.openstreetmap.org/wiki/QuadTiles#Quadtile_implementation)

## xyToIndex(x, y, [zoom])
 Convert x,y into a single integer with alternating bits
## indexToXY(index, [zoom])
 Convert index into the x,y coordinates (as a [x,y] array)
## isValidCoordinate(val, [zoom]), isValidIndex(index, [zoom]), isValidZoom(zoom)
 Boolean validation functions
## maxZoom
 Constant: Maximum supported zoom level (26)