LorenzBuehmann commented on issue #2219:
URL: https://github.com/apache/jena/issues/2219#issuecomment-1914140416
I don't see any negative implications, for me this is just fixing a bug -
indeed I might be wrong.
The crucial part in JTS is in class
Here they do
``` java
private void checkIntersectionWithSegments(LineString testLine)
{
CoordinateSequence seq1 = testLine.getCoordinateSequence();
Coordinate p0 = seq1.createCoordinate();
Coordinate p1 = seq1.createCoordinate();
for (int j = 1; j < seq1.size(); j++) {
seq1.getCoordinate(j - 1, p0);
seq1.getCoordinate(j, p1);
if (rectIntersector.intersects(p0, p1)) {
hasIntersection = true;
return;
}
}
}
```
the creation of new `Coordinates` comes from the default method in the
`CoordinateSequence` interface and does nothing more than taking into account
the dimensions of coordinate and the measure:
``` java
default Coordinate createCoordinate() {
return Coordinates.create(getDimension(), getMeasures());
}
```
Both are implemented in `CustomCoordinateSequence` correctly, i.e. the
dimension is 2 and measures is 0.
I'm sure it was simply forgotten to do a sanity check in the `getCoordinate`
method
``` java
@Override
public void getCoordinate(int index, Coordinate coord) {
coord.setX(x[index]);
coord.setY(y[index]);
coord.setZ(z[index]);
}
```
and by the way for some reason `setM` was not called - maybe also forgotten.
In any case checking for either the class type or just the dimension should
be the correct way in my opinion.
So either explicitly check for the Java type or for combination of
dimension/measure should at least fix the error. In JTS they do it by
``` java
public static Coordinate create(int dimension, int measures)
{
if (dimension == 2) {
return new CoordinateXY();
} else if (dimension == 3 && measures == 0) {
return new Coordinate();
} else if (dimension == 3 && measures == 1) {
return new CoordinateXYM();
} else if (dimension == 4 && measures == 1) {
return new CoordinateXYZM();
}
return new Coordinate();
}
```
It's confusing how JTS does handle the case `dim=3` and `measure=1` as Z
seems to be ignored:
> This data object is suitable for use with coordinate sequences with
dimension = 3 and measures = 1.
The Coordinate.z field is visible, but intended to be ignored
Long story short, we could adapt this with
``` java
@Override
public void getCoordinate(int index, Coordinate coord) {
coord.setX(x[index]);
coord.setY(y[index]);
if (coordinateDimension == 3 && measuresDimension == 0) {
coord.setZ(z[index]);
} else if (coordinateDimension == 3 && measuresDimension == 1) {
coord.setM(m[index]);
} else if (coordinateDimension == 4 && measuresDimension == 1) {
coord.setZ(z[index]);
coord.setM(m[index]);
}
}
```
Opinions?
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