PROOF.mask_len: def of bend-osdev-hashes@0.1.0.0
Import: import bend-osdev-hashes@0.1.0.0/PROOF.bend as PROOF
Lines 28-36 of bend-osdev-hashes@0.1.0.0/PROOF.bend: https://jend.leeeet.dev/read.txt?path=bend-osdev-hashes@0.1.0.0/PROOF.bend&start_line=28&end_line=36

import Base
import bend-osdev-bytes@0.1.0.0/bytes.bend as B

# Lengths: an Octets made from a list has the list's length; the bytes of
# a chaining value are a list of fixed shape whatever its words are
def mask_len(xs: List<&2, U32>) -> {B.len(B.mask(xs)) == B.len(xs) : Nat}:
  match xs:
    case Nil{}:
      {==}
    case Con{h, t}:
      %mask_len(t) : {B.len(B.mask(Con{h, t})) == 1n+_ : Nat}
      {==}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  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=bend-osdev-bytes@0.1.1.0/bytes.bend&name=len
  https://jend.leeeet.dev/definition.txt?path=bend-osdev-bytes@0.1.1.0/bytes.bend&name=mask