IntrusiveList.two_head: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/containers/internal/intrusive_list.bend as IntrusiveList
Lines 120-123 of bend-collections@1.0.0.0/src/containers/internal/intrusive_list.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/containers/internal/intrusive_list.bend&start_line=120&end_line=123

import Base

def two_head(~S: Type, ~N: Data, ~next: S -> N -> S & Maybe<&2, N>, s: S, +head: Maybe<&2, N>) -> S & Bool:
  match head:
    case None{}: (s, False{})
    case Some{n}: nonempty_result(~S, ~N, next(s, n))

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  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-collections@1.0.0.0/src/containers/internal/intrusive_list.bend&name=nonempty_result