Defs.join: def of lawful-fields@0.1.1.0
Import: import lawful-fields@0.1.1.0/defs.bend as Defs
Lines 133-141 of lawful-fields@0.1.1.0/defs.bend: https://jend.leeeet.dev/read.txt?path=lawful-fields@0.1.1.0/defs.bend&start_line=133&end_line=141

import Base

# The pieces joined with sep between them. join undoes split:
# join(split(xs, sep), sep) == xs (the other way round fails when a piece holds
# sep).
def join(ps: List<&2, List<&2, U32>>, +sep: U32) -> List<&2, U32>:
  match ps:
    case Nil{}:
      Nil{}
    case Con{p, t}:
      List.append(&2, U32, p, join.go(t, sep))

Uses (4):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.append
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=lawful-fields@0.1.1.0/defs.bend&name=join.go