∀ i. i ∈ ints → 0 ≤ i ∧ i < j, 0 ≤ j, j < n→i(# ints) ⊦ dups(ints)
Type: A user defined theorem
Validity: The proof is valid.
Features:
Comment: This is one version of the pidgeon hole principle.
The precondition 0 ≤ j implies that the list is
not empty and could be replaced by the
condition ints ≠ [].