Regex.required.prefix: def of bend-kit-regex@0.8.0.0
Import: import bend-kit-regex@0.8.0.0/regex.bend as Regex
Lines 577-589 of bend-kit-regex@0.8.0.0/regex.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-regex@0.8.0.0/regex.bend&start_line=577&end_line=589

import Base

# The first iteration contains the selected literal; every occurrence is inspected.
def required.prefix(n: Node) -> Maybe<&2, Node>:
  match n:
    case NSet{False{}, Con{Rng{+lo, +hi}, Nil{}}}:
      Bool.pick(Maybe<&2, Node>, U32.is_eq(lo, hi) && U32.is_lt(lo, 128), Some{lit(lo)}, None{})
    case NCat{+a, b}:
      required.join(required.prefix(b), required.prefix(a), a)
    case NPlus{g, a}:
      required.prefix(a)
    case NGroup{i, a}:
      required.prefix(a)
    case _:
      None{}

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.pick
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_eq
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_lt
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=Item
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=Node
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=lit
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=required.join