Tensor.is_perm: def of bendtorch@1.3.0.0
Import: import bendtorch@1.3.0.0/tensor.bend as Tensor
Lines 491-494 of bendtorch@1.3.0.0/tensor.bend: https://jend.leeeet.dev/read.txt?path=bendtorch@1.3.0.0/tensor.bend&start_line=491&end_line=494

import Base

# p is a permutation of the axes of a rank-n tensor
def is_perm(+p: List<&2, Nat>, +n: Nat) -> Bool:
  # bend-lint: disable-next bend-lint-rules/performance/eager_branch -- a shape predicate over a list of rank <= 4, once per operation; the types and LAWS.bend read its Bool form not-expected-because: a match would change the definition the proofs reduce, for no measurable gain
  Bool.and(Nat.is_eq(List.length(&2, Nat, p), n), all_once(n, p, 0n))

Uses (7):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.length
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.is_eq
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=all_once