Goal: Of the interpolated line, extract every other line segment, defined by the circles. In the example, these are the long line segments, i.e. the ones between circles 0 and 1, and between circles 2 and 3. (In reality, there are a lot more circles.)
As you can see, I tried combining Curve | Curve intersection with Shatter. While the result contains the line segment between circles 0 and 1, the line segment between circles 2 and 3 is missing.
Interestingly, when opening your file in Grasshopper WIP, then I get error messages:
The errors can be removed by deleting an invisible character at the end of each lιst in the yellow panels. It almost looks like there is an issue with Mac vs. Windows line endings. Did you use Mac Grasshopper?