lean4-htt/tests/lean/run/grind_getLast_dropLast.lean
Leonardo de Moura bcc6fb54c2
perf: use inShareCommon to skip preprocessing steps (#9351)
This PR optimizes the `grind` preprocessing steps by skipping steps when
the term is already present in the hash-consing table.
2025-07-14 04:53:49 +00:00

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reset_grind_attrs%
open List
theorem length_pos_of_ne_nil {l : List α} (h : l ≠ []) : 0 < l.length := by
cases l <;> simp_all
theorem getLast?_dropLast {xs : List α} :
xs.dropLast.getLast? = if xs.length ≤ 1 then none else xs[xs.length - 2]? := by
grind (splits := 23) only [List.getElem?_eq_none, List.getElem?_reverse, getLast?_eq_getElem?,
List.head?_eq_getLast?_reverse, getElem?_dropLast, List.getLast?_reverse, List.length_dropLast,
List.length_reverse, length_nil, List.reverse_reverse, head?_nil, List.getElem?_eq_none,
getLast?_nil, List.head?_reverse, List.getLast?_eq_head?_reverse, = List.getElem?_nil, reverse_nil, cases Or]