Topology.sumd2_count: def of bend-prot@0.1.0.0
Import: import bend-prot@0.1.0.0/topology.bend as Topology
Lines 61-67 of bend-prot@0.1.0.0/topology.bend: https://jend.leeeet.dev/read.txt?path=bend-prot@0.1.0.0/topology.bend&start_line=61&end_line=67

import Base
import bend-prot@0.1.0.0/geom.bend as G
import bend-prot@0.1.0.0/protein.bend as P

# One pass: summed squared distances about qp, plus atom count.
def sumd2_count(xs: List<&2, P.Atom>, +qp: G.Vec3) -> F32 & Nat:
  match xs:
    case Nil{}:
      (0.0, 0n)
    case h <> t:
      sumd2_extend(head_dist2(h, qp), sumd2_count(t, qp))

Uses (9):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=bend-prot@0.1.0.0/geom.bend&name=Vec3
  https://jend.leeeet.dev/definition.txt?path=bend-prot@0.1.0.0/protein.bend&name=Atom
  https://jend.leeeet.dev/definition.txt?path=bend-prot@0.1.0.0/topology.bend&name=head_dist2
  https://jend.leeeet.dev/definition.txt?path=bend-prot@0.1.0.0/topology.bend&name=sumd2_extend