GEOS
3.8.0dev

Provides a test for whether an interval is so small it should be considered as zero for the purposes of inserting it into a binary tree. More...
#include <geos/indexQuadtree.h>
Static Public Member Functions  
static bool  isZeroWidth (double min, double max) 
Static Public Attributes  
static const int  MIN_BINARY_EXPONENT = 50 
Provides a test for whether an interval is so small it should be considered as zero for the purposes of inserting it into a binary tree.
The reason this check is necessary is that roundoff error can cause the algorithm used to subdivide an interval to fail, by computing a midpoint value which does not lie strictly between the endpoints.

static 
Computes whether the interval [min, max] is effectively zero width. I.e. the width of the interval is so much less than the location of the interval that the midpoint of the interval cannot be represented precisely.

static 
This value is chosen to be a few powers of 2 less than the number of bits available in the double representation (i.e. 53). This should allow enough extra precision for simple computations to be correct, at least for comparison purposes.