Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
02ca710872
This PR adds support the Count Trailing Zeros operation `BitVec.ctz` to the bitvector library and to `bv_decide`, relying on the existing `clz` circuit. We also build some theory around `BitVec.ctz` (analogous to the theory existing for `BitVec.clz`) and introduce lemmas `BitVec.[ctz_eq_reverse_clz, clz_eq_reverse_ctz, ctz_lt_iff_ne_zero, getLsbD_false_of_lt_ctz, getLsbD_true_ctz_of_ne_zero, two_pow_ctz_le_toNat_of_ne_zero, reverse_reverse_eq, reverse_eq_zero_iff]`. `ctz` operation is common in numerous compiler intrinsics (see [here](https://clang.llvm.org/docs/LanguageExtensions.html#intrinsics-support-within-constant-expressions)) and architectures (see [here](https://en.wikipedia.org/wiki/Find_first_set)). --------- Co-authored-by: Siddharth <siddu.druid@gmail.com> |
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