Hylograph.Expr.Path

class PathExpr :: (Type -> Type) -> Constraintclass PathExpr repr  where

Path expressions - generate SVG path strings

Each interpreter handles these differently:

• Eval: computes the actual path string
• CodeGen: generates (linkHorizontal x1 y1 x2 y2)
• SVG: computes the path string (same as Eval for paths)

Members

• linePath :: repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Straight line from (x1,y1) to (x2,y2) Generates: "M x1,y1 L x2,y2"

• polylinePath :: repr (Array { x :: Number, y :: Number }) -> repr String

  Polyline through multiple points Takes array of {x, y} points Generates: "M x0,y0 L x1,y1 L x2,y2 ..."

• linkHorizontal :: repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Horizontal link with cubic bezier (left-to-right trees) Control points at horizontal midpoint

   source ----╮
              ╰---- target
  

  Generates: "M x1,y1 C mx,y1 mx,y2 x2,y2" where mx = (x1+x2)/2

• linkVertical :: repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Vertical link with cubic bezier (top-down trees) Control points at vertical midpoint

      source
         |
         ╰---╮
             target
  

  Generates: "M x1,y1 C x1,my x2,my x2,y2" where my = (y1+y2)/2

• linkRadial :: repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Radial link for radial/circular tree layouts Takes angles (radians) and radii instead of x,y

  Generates curved path from (angle1, radius1) to (angle2, radius2)

• sankeyLink :: repr Number -> repr Number -> repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Sankey-style horizontal flow link Like linkHorizontal but with variable width (y0/y1 at each end)

   ╭──────────╮
   │  flow    │
   ╰──────────╯
  

  Generates a filled shape (not just a stroke path)

• ribbon :: repr Number -> repr Number -> repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Ribbon for chord diagrams Connects two arcs on a circle with curved bands

  Takes: source arc (startAngle, endAngle), target arc (startAngle, endAngle), radius

  The ribbon is a closed shape suitable for fill

• arc :: repr Number -> repr Number -> repr Number -> repr Number -> repr String

  Arc segment (for pie/donut charts, chord diagram outer ring)

  Generates arc from startAngle to endAngle at given radii Closed shape suitable for fill

• closePath :: repr String -> repr String

  Append "Z" to close a path