Size.retains: def of bendtorch-core@0.1.0.0
Import: import bendtorch-core@0.1.0.0/src/storage/size.bend as Size
Lines 41-48 of bendtorch-core@0.1.0.0/src/storage/size.bend: https://jend.leeeet.dev/read.txt?path=bendtorch-core@0.1.0.0/src/storage/size.bend&start_line=41&end_line=48

import Base

def retains(-T: Data, -d: Nat, -original: Array<T>, sized: Sized<T, d, original>) ->
  {Pair.fst(Array<T>, U32, Array.size(T, original)) == original : Array<T>}:
  match sized:
    case Sized{array, n, retained, measured, extent, balanced}:
      Equal.trans(Array<T>, Pair.fst(Array<T>, U32, Array.size(T, original)), array, original,
        Equal.cong(Array<T> & U32, Array<T>, r => Pair.fst(Array<T>, U32, r),
          Array.size(T, original), (array, n),
          Equal.sym(Array<T> & U32, (array, n), Array.size(T, original), measured)), retained)

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.size
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.cong
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.sym
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.trans
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair.fst
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/storage/size.bend&name=Sized