Survival.keep_nat: def of unified-nsga-iii@0.2.2.0
Import: import unified-nsga-iii@0.2.2.0/survival.bend as Survival
Lines 115-120 of unified-nsga-iii@0.2.2.0/survival.bend: https://jend.leeeet.dev/read.txt?path=unified-nsga-iii@0.2.2.0/survival.bend&start_line=115&end_line=120

import Base

def keep_nat(h: Nat, rest: List<&2, Nat>, keep: Bool) -> List<&2, Nat>:
  match keep:
    case True{}:
      h <> rest
    case False{}:
      rest

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat