[mkgmap-dev] Question reg. LinePreparer

Tue Feb 5 07:38:42 GMT 2013

Hi,

I simply copied it to the LinePreparerFilter, but what is the idea behind
this code in LinePreparer?

			// compute normalized differences
			//   -2^(shift-1) <= dx, dy < 2^(shift-1)
			// XXX: relies on the fact that java integers are 32 bit signed
			final int offset = 8+shift;
			int dx = (lon - lastLong) << offset >> offset;
			int dy = (lat - lastLat) << offset >> offset;

I don't understand the comment. Why are the values shifted left and right? 
While debugging I did not see a case where this changed the result. 

Gerd

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