Regex.first: def of bend-kit-regex@0.8.0.0
Import: import bend-kit-regex@0.8.0.0/regex.bend as Regex
Lines 757-769 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=757&end_line=769

import Base

# fuel: each pc expands once and pushes at most two pcs.
def first(fuel: Nat, +prog: List<&2, Inst>, st: Fs) -> Maybe<&2, List<&2, Inst>>:
  match fuel:
    case 0n:
      None{}
    case 1n+f:
      match st:
        case FsAny{}:
          None{}
        case Fs{Nil{}, seen, sets}:
          Some{sets}
        case Fs{Con{+pc, t}, +seen, sets}:
          first(f, prog, first.seen(List.contains(~U32, ~U32.is_eq, seen, pc), prog, pc, t, seen, sets))

Uses (9):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.contains
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.is_eq
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=Fs
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=Inst
  https://jend.leeeet.dev/definition.txt?path=bend-kit-regex@0.8.0.0/regex.bend&name=first.seen