Sim.back: def of bend-lawful-stdlib@0.1.0.0
Import: import bend-lawful-stdlib@0.1.0.0/src/sim.bend as Sim
Lines 27-31 of bend-lawful-stdlib@0.1.0.0/src/sim.bend: https://jend.leeeet.dev/read.txt?path=bend-lawful-stdlib@0.1.0.0/src/sim.bend&start_line=27&end_line=31

import Base
import bend-lawful-stdlib@0.1.0.0/src/class.bend as C

def back(~P: Data, ~g: C.Group<P>, ~F: P -> P, s: State<P>) -> State<P>:
  match s:
    case State{x, +w}:
      +x0 = C.Group.sub(P, g, x, w)
      State{x0, C.Group.sub(P, g, w, F(x0))}

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=bend-lawful-stdlib@0.1.0.0/src/class.bend&name=Group
  https://jend.leeeet.dev/definition.txt?path=bend-lawful-stdlib@0.1.0.0/src/class.bend&name=Group.sub
  https://jend.leeeet.dev/definition.txt?path=bend-lawful-stdlib@0.1.0.0/src/sim.bend&name=State