lean4-htt/src/Init/SizeOfLemmas.lean
Henrik Böving 19e06acc65
refactor: redefine unsigned fixed width integers in terms of BitVec (#5323)
I made a few choices so far that can probably be discussed:
- got rid of `modn` on `UInt`, nobody seems to use it apart from the
definition of `shift` which can use normal `mod`
- removed the previous defeq optimized definition of `USize.size` in
favor for a normal one. The motivation was to allow `OfNat` to work
which doesn't seem to be necessary anymore afaict.
- Minimized uses of `.val`, should we maybe mark it deprecated?
- Mostly got rid of `.val` in basically all theorems as the proper next
level of API would now be `.toBitVec`. We could probably re-prove them
but it would be more annoying given the change of definition.
- Did not yet redefine `log2` in terms of `BitVec` as this would require
a `log2` in `BitVec` as well, do we want this?
- I added a couple of theorems around the relation of `<` on `UInt` and
`Nat`. These were previously not needed because defeq was used all over
the place to save us. I did not yet generalize these to all types as I
wasn't sure if they are the appropriate lemma that we want to have.
2024-10-16 07:28:23 +00:00

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/-
Copyright (c) 2022 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
prelude
import Init.Meta
import Init.SizeOf
import Init.Data.Nat.Linear
@[simp] protected theorem Fin.sizeOf (a : Fin n) : sizeOf a = a.val + 1 := by
cases a; simp_arith
@[simp] protected theorem BitVec.sizeOf (a : BitVec w) : sizeOf a = sizeOf a.toFin + 1 := by
cases a; simp_arith
@[simp] protected theorem UInt8.sizeOf (a : UInt8) : sizeOf a = a.toNat + 3 := by
cases a; simp_arith [UInt8.toNat, BitVec.toNat]
@[simp] protected theorem UInt16.sizeOf (a : UInt16) : sizeOf a = a.toNat + 3 := by
cases a; simp_arith [UInt16.toNat, BitVec.toNat]
@[simp] protected theorem UInt32.sizeOf (a : UInt32) : sizeOf a = a.toNat + 3 := by
cases a; simp_arith [UInt32.toNat, BitVec.toNat]
@[simp] protected theorem UInt64.sizeOf (a : UInt64) : sizeOf a = a.toNat + 3 := by
cases a; simp_arith [UInt64.toNat, BitVec.toNat]
@[simp] protected theorem USize.sizeOf (a : USize) : sizeOf a = a.toNat + 3 := by
cases a; simp_arith [USize.toNat, BitVec.toNat]
@[simp] protected theorem Char.sizeOf (a : Char) : sizeOf a = a.toNat + 4 := by
cases a; simp_arith [Char.toNat]
@[simp] protected theorem Subtype.sizeOf {α : Sort u_1} {p : α → Prop} (s : Subtype p) : sizeOf s = sizeOf s.val + 1 := by
cases s; simp