List.map_map_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/list.bend as List
Lines 2261-2269 of bend-mathlib@0.8.1.0/list.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/list.bend&start_line=2261&end_line=2269

import Base

# Mapping twice is mapping the composition: map g (map f xs) = map (g . f) xs, reversed to rewrite toward the simple side.
law map_map_sym:
  for ~A: Type
  for ~B: Type
  for ~C: Type
  for ~f: A -> B
  for ~g: B -> C
  for xs: List<A>
  {List.map(~A, ~C, ~(x => g(f(x))), xs) == List.map(~B, ~C, ~g, List.map(~A, ~B, ~f, xs)) : List<C>}

Uses (4):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.sym
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.map
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/list.bend&name=map_map