bitmask representation of lte

This commit is contained in:
rhiannon morris 2022-11-05 22:08:57 +01:00
parent 53bbcbf8c7
commit 4b64399891
2 changed files with 194 additions and 44 deletions

View file

@ -1,7 +1,9 @@
module Quox.NatExtra
import public Data.Nat
import Data.Nat.Division
import public Data.Nat.Properties
import public Data.Nat.Division
import Data.DPair
import Data.SnocList
import Data.Vect
@ -68,7 +70,7 @@ divNatViaInteger m n = i2n $ n2i m `div` n2i n
private %inline
divNatViaIntegerNZ : (m, n : Nat) -> (0 _ : NonZero n) -> Nat
divNatViaIntegerNZ m n _ = assert_total divNatViaInteger m n
%transform "divNat" divNatNZ = divNatViaIntegerNZ
%transform "divNatNZ" divNatNZ = divNatViaIntegerNZ
private partial %inline
modNatViaInteger : (m, n : Nat) -> Nat
@ -78,24 +80,62 @@ modNatViaInteger m n = i2n $ n2i m `mod` n2i n
private %inline
modNatViaIntegerNZ : (m, n : Nat) -> (0 _ : NonZero n) -> Nat
modNatViaIntegerNZ m n _ = assert_total modNatViaInteger m n
%transform "modNat" modNatNZ = modNatViaIntegerNZ
%transform "modNatNZ" modNatNZ = modNatViaIntegerNZ
public export
data ViewLsb : Nat -> Type where
Lsb0 : (n : Nat) -> ViewLsb (2 * n)
Lsb1 : (n : Nat) -> ViewLsb (S (2 * n))
data Parity = Even | Odd
public export
data ViewLsb : Nat -> Parity -> Type where
Lsb0 : (n : Nat) -> ViewLsb (2 * n) Even
Lsb1 : (n : Nat) -> ViewLsb (S (2 * n)) Odd
%name ViewLsb p, q
export
fromLsb0 : ViewLsb n Even -> Subset Nat (\n' => n = 2 * n')
fromLsb0 (Lsb0 n') = Element n' Refl
export
fromLsb1 : ViewLsb n Odd -> Subset Nat (\n' => n = S (2 * n'))
fromLsb1 (Lsb1 n') = Element n' Refl
private
viewLsb' : (m, d : Nat) -> (0 _ : m `LT` 2) -> ViewLsb (m + 2 * d)
viewLsb' 0 d p = Lsb0 d
viewLsb' 1 d p = Lsb1 d
viewLsb' : (m, d : Nat) -> (0 _ : m `LT` 2) -> Exists $ ViewLsb (m + 2 * d)
viewLsb' 0 d p = Evidence Even (Lsb0 d)
viewLsb' 1 d p = Evidence Odd (Lsb1 d)
viewLsb' (S (S _)) _ (LTESucc p) = void $ absurd p
export
viewLsb : (n : Nat) -> ViewLsb n
viewLsb : (n : Nat) -> Exists $ ViewLsb n
viewLsb n =
let nz = the (NonZero 2) %search in
let 0 nz = the (NonZero 2) %search in
rewrite DivisionTheorem n 2 nz nz in
rewrite multCommutative (divNatNZ n 2 nz) 2 in
viewLsb' (modNatNZ n 2 nz) (divNatNZ n 2 nz) (boundModNatNZ n 2 nz)
export
0 lsbMutex' : n = (2 * a) -> n = S (2 * b) -> Void
lsbMutex' ev od {n = 0} impossible
lsbMutex' ev od {n = 1} {a = S a} {b = 0} =
let ev = injective ev in
let s = sym $ plusSuccRightSucc a (a + 0) in
absurd $ trans ev s
lsbMutex' ev od {n = S (S n)} {a = S a} {b = S b} =
let ev = injective $
trans (injective ev) (sym $ plusSuccRightSucc a (a + 0)) in
let od = trans (injective $ injective od)
(sym $ plusSuccRightSucc b (b + 0)) in
lsbMutex' ev od
export
0 lsbMutex : ViewLsb n Even -> ViewLsb n Odd -> Void
lsbMutex p q = lsbMutex' (fromLsb0 p).snd (fromLsb1 q).snd
export
doubleInj : {m, n : Nat} -> 2 * m = 2 * n -> m = n
doubleInj eq =
multRightCancel m n 2 %search $
trans (multCommutative m 2) $ trans eq (multCommutative 2 n)

View file

@ -42,15 +42,23 @@ Uninhabited (xs :< x `LTE` xs) where
export
lteLen : xs `LTE` ys -> length xs `LTE_n` length ys
0 lteLen : xs `LTE` ys -> length xs `LTE_n` length ys
lteLen End = LTEZero
lteLen (Keep p) = LTESucc $ lteLen p
lteLen (Drop p) = lteSuccRight $ lteLen p
export
lteNilRight : xs `LTE` [<] -> xs = [<]
0 lteNilRight : xs `LTE` [<] -> xs = [<]
lteNilRight End = Refl
export
0 lteNilLeftDrop : (p : [<] `LTE` (xs :< x)) -> Exists (\q => p = Drop q)
lteNilLeftDrop (Drop q) = Evidence q Refl
export
0 lteNil2End : (p : [<] `LTE` [<]) -> p = End
lteNil2End End = Refl
public export
data Length : Scope a -> Type where
@ -59,6 +67,18 @@ data Length : Scope a -> Type where
%name Length s
%builtin Natural Length
namespace Length
public export
(.nat) : Length xs -> Nat
(Z).nat = Z
(S s).nat = S s.nat
%transform "Length.nat" Length.(.nat) xs = believe_me xs
export
0 lengthOk : (s : Length xs) -> s.nat = length xs
lengthOk Z = Refl
lengthOk (S s) = cong S $ lengthOk s
export %hint
lengthLeft : xs `LTE` ys -> Length xs
lengthLeft End = Z
@ -102,6 +122,119 @@ p ++ Keep q = Keep (p ++ q)
p ++ Drop q = Drop (p ++ q)
public export
data LTEMaskView : (lte : xs `LTE` ys) -> (mask : Nat) -> Type where
[search lte]
END : LTEMaskView End 0
KEEP : (0 _ : LTEMaskView p n) -> LTEMaskView (Keep p) (S (2 * n))
DROP : (0 _ : LTEMaskView p n) -> LTEMaskView (Drop p) (2 * n)
%name LTEMaskView p, q
record LTEMask {a : Type} (xs, ys : Scope a) where
constructor LTEM
mask : Nat
0 lte : xs `LTE` ys
0 view0 : LTEMaskView lte mask
%name LTEMask m
namespace View
private
0 lteMaskEnd' : LTEMaskView p n -> p = End -> n = 0
lteMaskEnd' END Refl = Refl
private
0 lteMaskDrop' : LTEMaskView p n -> p = Drop q -> (n' ** n = 2 * n')
lteMaskDrop' (DROP p {n = n'}) Refl = (n' ** Refl)
private
0 lteMaskEven' : {p : xs `LTE` (ys :< y)} ->
n = 2 * n' -> LTEMaskView p n -> (q ** p = Drop q)
lteMaskEven' eq (KEEP q) = absurd $ lsbMutex' eq Refl
lteMaskEven' eq (DROP q) = (_ ** Refl)
private
lteMaskEven : {0 p : xs `LTE` (ys :< y)} ->
(0 _ : LTEMaskView p (2 * n)) -> Exists (\q => p = Drop q)
lteMaskEven q =
let 0 res = lteMaskEven' Refl q in
Evidence res.fst (irrelevantEq res.snd)
private
0 fromDROP' : {lte : xs `LTE` ys} -> n = 2 * n' ->
LTEMaskView (Drop lte) n -> LTEMaskView lte n'
fromDROP' eq (DROP {n} p) =
let eq = doubleInj eq {m = n, n = n'} in
rewrite sym eq in p
private
0 fromDROP : LTEMaskView (Drop lte) (2 * n) -> LTEMaskView lte n
fromDROP = fromDROP' Refl
private
0 lteMaskOdd' : {p : (xs :< x) `LTE` (ys :< x)} -> {n' : Nat} ->
n = S (2 * n') -> LTEMaskView p n -> (q ** p = Keep q)
lteMaskOdd' eq (KEEP q) = (_ ** Refl)
lteMaskOdd' eq (DROP q) = absurd $ lsbMutex' Refl eq
lteMaskOdd' _ END impossible
private
lteMaskOdd : (0 _ : LTEMaskView p (S (2 * n))) -> Exists (\q => p = Keep q)
lteMaskOdd q =
let 0 res = lteMaskOdd' Refl q in
Evidence res.fst (irrelevantEq res.snd)
private
0 lteMaskOddHead' : {p : (xs :< x) `LTE` (ys :< y)} -> {n' : Nat} ->
n = S (2 * n') -> LTEMaskView p n -> x = y
lteMaskOddHead' eq (KEEP q) = Refl
lteMaskOddHead' eq (DROP q) = absurd $ lsbMutex' Refl eq
lteMaskOddHead' eq END impossible
private
lteMaskOddHead : {0 p : (xs :< x) `LTE` (ys :< y)} ->
(0 _ : LTEMaskView p (S (2 * n))) -> x = y
lteMaskOddHead q = irrelevantEq $ lteMaskOddHead' Refl q
private
0 fromKEEP' : {lte : xs `LTE` ys} -> n = S (2 * n') ->
LTEMaskView (Keep lte) n -> LTEMaskView lte n'
fromKEEP' eq (KEEP {n} p) =
let eq = doubleInj (injective eq) {m = n, n = n'} in
rewrite sym eq in p
private
0 fromKEEP : LTEMaskView (Keep lte) (S (2 * n)) -> LTEMaskView lte n
fromKEEP = fromKEEP' Refl
export
view : (sx : Length xs) => (sy : Length ys) =>
(m : LTEMask xs ys) -> LTEMaskView m.lte m.mask
view @{Z} @{Z} (LTEM {lte, view0, _}) =
rewrite lteNil2End lte in
rewrite lteMaskEnd' view0 (lteNil2End lte) in
END
view @{S _} @{Z} (LTEM {lte, _}) = void $ absurd lte
view @{Z} @{S sy} (LTEM mask lte view0) =
rewrite (lteNilLeftDrop lte).snd in
rewrite (lteMaskDrop' view0 (lteNilLeftDrop lte).snd).snd in
DROP $ let DROP p = view0 in p
view @{S sx} @{S sy} (LTEM mask lte view0) with (viewLsb mask)
view @{S sx} @{S sy} (LTEM (2 * n) lte view0)
| Evidence Even (Lsb0 n) with (lteMaskEven view0)
view @{S sx} @{S sy} (LTEM (2 * m) (Drop lte) view0)
| Evidence Even (Lsb0 m) | Evidence lte Refl =
DROP $ fromDROP view0
view @{S sx} @{S sy} (LTEM (S (2 * n)) lte view0)
| Evidence Odd (Lsb1 n) with (lteMaskOddHead view0)
view @{S sx} @{S sy} (LTEM (S (2 * n)) lte view0)
| Evidence Odd (Lsb1 n) | Refl with (lteMaskOdd view0)
view @{S sx} @{S sy} (LTEM (S (2 * n)) (Keep lte) view0)
| Evidence Odd (Lsb1 n) | Refl | Evidence lte Refl =
KEEP $ fromKEEP view0
public export
record Split {a : Type} (xs, ys, zs : Scope a) (p : xs `LTE` ys ++ zs) where
constructor MkSplit
@ -165,15 +298,6 @@ compIdRight {sx = S _} (Keep p) = CKK (compIdRight p)
compIdRight (Drop p) = CD0 (compIdRight p)
private
0 compExample :
Comp {zs = [< a, b, c, d, e]}
(Keep $ Drop $ Keep $ Drop $ Keep End)
(Keep $ Drop $ Keep End)
(Keep $ Drop $ Drop $ Drop $ Keep End)
compExample = %search
export
0 compAssoc : (p : ys `LTE` zs) -> (q : xs `LTE` ys) -> (r : ws `LTE` xs) ->
p . (q . r) = (p . q) . r
@ -191,20 +315,23 @@ Scoped a = Scope a -> Type
public export
Subscope : Scope a -> Type
Subscope xs = Exists (`LTE` xs)
Subscope ys = Exists (`LTE` ys)
public export
SubMap : {xs, ys : Scope a} -> xs `LTE` zs -> ys `LTE` zs -> Type
SubMap p q = DPair (xs `LTE` ys) (\r => Comp q r p)
record SubMap {a : Type} {xs, ys, zs : Scope a}
(p : xs `LTE` zs) (q : ys `LTE` zs) where
constructor SM
thin : xs `LTE` ys
0 comp : Comp q thin p
parameters (p : xs `LTE` ys)
export
subId : SubMap p p
subId = (id ** compIdRight p)
subId = SM id (compIdRight p)
export
subZero : SubMap OPE.zero p
subZero = (zero ** compZero p)
subZero = SM zero (compZero p)
public export
@ -240,20 +367,3 @@ public export
Partition : xs `LTE` zs -> ys `LTE` zs -> Type
Partition = Cover_ False
public export
data LTEMaskView : xs `LTE` ys -> Nat -> Type where
END : LTEMaskView End 0
KEEP : (0 _ : LTEMaskView p n) -> LTEMaskView (Keep p) (S (2 * n))
DROP : (0 _ : LTEMaskView p n) -> LTEMaskView (Drop p) (2 * n)
record LTEMask {a : Type} (xs, ys : Scope a) where
constructor LTEM
mask : Nat
0 lte : xs `LTE` ys
0 view0 : LTEMaskView lte mask
export
view : (sx : Length xs) => (sy : Length ys) =>
(m : LTEMask xs ys) -> LTEMaskView m.lte m.mask