String.append_assoc_sym: law of bend-mathlib@0.8.1.0
Import: import bend-mathlib@0.8.1.0/string.bend as String
Lines 548-553 of bend-mathlib@0.8.1.0/string.bend: https://jend.leeeet.dev/read.txt?path=bend-mathlib@0.8.1.0/string.bend&start_line=548&end_line=553

import Base

# Append is associative: (a ++ b) ++ c = a ++ (b ++ c), reversed to rewrite toward the simple side.
law append_assoc_sym:
  for a: String
  for -b: String
  for -c: String
  {String.append(a, String.append(b, c)) == String.append(String.append(a, b), c) : String}

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=String
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.append
  https://jend.leeeet.dev/definition.txt?path=bend-mathlib@0.8.1.0/string.bend&name=append_assoc