Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
ba8c2ed4ee
This PR adds `simpArrowTelescope`, a simproc that simplifies telescopes of non-dependent arrows (p₁ → p₂ → ... → q) while avoiding quadratic proof growth. When using `Expr.forallE` to represent nested implications, each nesting level bumps de Bruijn indices in subterms, destroying sharing even with hash-consing. For example, a free variable `x` gets different de Bruijn representations at each depth, causing proof terms to grow. `simpArrowTelescope` works by: - Converting arrows to `Arrow p q` (a definitional wrapper) - Simplifying each component - Converting back to `→` form Since `Arrow` arguments are not under binders, subterms remain identical across nesting levels and can be shared. The `simp_4` benchmark demonstrates the improvement: With `forallE`: ~160ms, proof_size ≈ 173k With `Arrow`: ~43ms, proof_size ≈ 16k Tradeoff: `simpArrowTelescope` misses simplifications that depend on the arrow structure (e.g., `p → p` to `True`), since post-methods aren't applied to intermediate arrows. Thus, it is not used by default. to use it, one has to set `simpArrowTelescope` as a `pre`-method. |
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