QGIS/resources/function_help/json/distance_to_vertex

{
  "name": "distance_to_vertex",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Returns the distance along the geometry to a specified vertex.",
  "arguments": [ {"arg":"geometry","description":"a linestring geometry"},
                 {"arg":"vertex","description":"vertex index, starting from 0; if the value is negative, the selected vertex index will be its total count minus the absolute value"}],
  "examples": [ { "expression":"distance_to_vertex(geometry:=geom_from_wkt('LineString(0 0, 10 0, 10 10)'),vertex:=1)", "returns":"10.0"}]
}