DynamicArray.clear_go_at: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/containers/dynamic_array.bend as DynamicArray
Lines 423-434 of bend-collections@1.0.0.0/src/containers/dynamic_array.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/containers/dynamic_array.bend&start_line=423&end_line=434

import Base

# The executable clear resets the occupied slots [0, length) to None, top
# down, and keeps the block: O(length), no allocation. Dropping the old block
# and allocating a fresh one (what the parametric `clear` describes) walks
# every one of the 2^depth slots twice in the runtime. Every slot at or past
# the length already holds None, so the result is the same all-None block;
# proofs/containers/dynamic_array/clear.bend proves it on every good state.
def clear_go_at(~T: Data, k: Nat, arr: Array<Maybe<&2, T>>) -> Array<Maybe<&2, T>>:
  match k:
    case 0n:
      arr
    case 1n+ +m:
      clear_go_at(~T, m, Array.set(Maybe<&2, T>, arr, U32.from_nat(m), None{}))

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.set
  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.from_nat