Share 'Custom Polyline GraphMapper. How?'

Dear Grasshoppers. I'd like to use a polyline as a GraphMapper curve, like this: I would like to check the Y value of the polyline at regular X-intervals.   I could create a bunch of lines and intersect them with the polyline to get points, but is there a more "mathematical" way? Evaluate curve wouldn't work because then it wouldn't be even steps along the X-axes. Any ideas? Thanks!