(* Title: HOL/Library/Word.thy
ID: $Id$
Author: Sebastian Skalberg (TU Muenchen)
*)
header {* Binary Words *}
theory Word
imports List
begin
subsection {* Auxilary Lemmas *}
lemma max_le [intro!]: "[| x \<le> z; y \<le> z |] ==> max x y \<le> z"
by (simp add: max_def)
lemma max_mono:
fixes x :: "'a::linorder"
assumes mf: "mono f"
shows "max (f x) (f y) \<le> f (max x y)"
proof -
from mf and le_maxI1 [of x y]
have fx: "f x \<le> f (max x y)" by (rule monoD)
from mf and le_maxI2 [of y x]
have fy: "f y \<le> f (max x y)" by (rule monoD)
from fx and fy
show "max (f x) (f y) \<le> f (max x y)" by auto
qed
declare zero_le_power [intro]
and zero_less_power [intro]
lemma int_nat_two_exp: "2 ^ k = int (2 ^ k)"
by (simp add: zpower_int [symmetric])
subsection {* Bits *}
datatype bit =
Zero ("\<zero>")
| One ("\<one>")
consts
bitval :: "bit => nat"
primrec
"bitval \<zero> = 0"
"bitval \<one> = 1"
consts
bitnot :: "bit => bit"
bitand :: "bit => bit => bit" (infixr "bitand" 35)
bitor :: "bit => bit => bit" (infixr "bitor" 30)
bitxor :: "bit => bit => bit" (infixr "bitxor" 30)
notation (xsymbols)
bitnot ("\<not>\<^sub>b _" [40] 40) and
bitand (infixr "\<and>\<^sub>b" 35) and
bitor (infixr "\<or>\<^sub>b" 30) and
bitxor (infixr "\<oplus>\<^sub>b" 30)
notation (HTML output)
bitnot ("\<not>\<^sub>b _" [40] 40) and
bitand (infixr "\<and>\<^sub>b" 35) and
bitor (infixr "\<or>\<^sub>b" 30) and
bitxor (infixr "\<oplus>\<^sub>b" 30)
primrec
bitnot_zero: "(bitnot \<zero>) = \<one>"
bitnot_one : "(bitnot \<one>) = \<zero>"
primrec
bitand_zero: "(\<zero> bitand y) = \<zero>"
bitand_one: "(\<one> bitand y) = y"
primrec
bitor_zero: "(\<zero> bitor y) = y"
bitor_one: "(\<one> bitor y) = \<one>"
primrec
bitxor_zero: "(\<zero> bitxor y) = y"
bitxor_one: "(\<one> bitxor y) = (bitnot y)"
lemma bitnot_bitnot [simp]: "(bitnot (bitnot b)) = b"
by (cases b) simp_all
lemma bitand_cancel [simp]: "(b bitand b) = b"
by (cases b) simp_all
lemma bitor_cancel [simp]: "(b bitor b) = b"
by (cases b) simp_all
lemma bitxor_cancel [simp]: "(b bitxor b) = \<zero>"
by (cases b) simp_all
subsection {* Bit Vectors *}
text {* First, a couple of theorems expressing case analysis and
induction principles for bit vectors. *}
lemma bit_list_cases:
assumes empty: "w = [] ==> P w"
and zero: "!!bs. w = \<zero> # bs ==> P w"
and one: "!!bs. w = \<one> # bs ==> P w"
shows "P w"
proof (cases w)
assume "w = []"
thus ?thesis by (rule empty)
next
fix b bs
assume [simp]: "w = b # bs"
show "P w"
proof (cases b)
assume "b = \<zero>"
hence "w = \<zero> # bs" by simp
thus ?thesis by (rule zero)
next
assume "b = \<one>"
hence "w = \<one> # bs" by simp
thus ?thesis by (rule one)
qed
qed
lemma bit_list_induct:
assumes empty: "P []"
and zero: "!!bs. P bs ==> P (\<zero>#bs)"
and one: "!!bs. P bs ==> P (\<one>#bs)"
shows "P w"
proof (induct w, simp_all add: empty)
fix b bs
assume "P bs"
then show "P (b#bs)"
by (cases b) (auto intro!: zero one)
qed
definition
bv_msb :: "bit list => bit" where
"bv_msb w = (if w = [] then \<zero> else hd w)"
definition
bv_extend :: "[nat,bit,bit list]=>bit list" where
"bv_extend i b w = (replicate (i - length w) b) @ w"
definition
bv_not :: "bit list => bit list" where
"bv_not w = map bitnot w"
lemma bv_length_extend [simp]: "length w \<le> i ==> length (bv_extend i b w) = i"
by (simp add: bv_extend_def)
lemma bv_not_Nil [simp]: "bv_not [] = []"
by (simp add: bv_not_def)
lemma bv_not_Cons [simp]: "bv_not (b#bs) = (bitnot b) # bv_not bs"
by (simp add: bv_not_def)
lemma bv_not_bv_not [simp]: "bv_not (bv_not w) = w"
by (rule bit_list_induct [of _ w]) simp_all
lemma bv_msb_Nil [simp]: "bv_msb [] = \<zero>"
by (simp add: bv_msb_def)
lemma bv_msb_Cons [simp]: "bv_msb (b#bs) = b"
by (simp add: bv_msb_def)
lemma bv_msb_bv_not [simp]: "0 < length w ==> bv_msb (bv_not w) = (bitnot (bv_msb w))"
by (cases w) simp_all
lemma bv_msb_one_length [simp,intro]: "bv_msb w = \<one> ==> 0 < length w"
by (cases w) simp_all
lemma length_bv_not [simp]: "length (bv_not w) = length w"
by (induct w) simp_all
definition
bv_to_nat :: "bit list => nat" where
"bv_to_nat = foldl (%bn b. 2 * bn + bitval b) 0"
lemma bv_to_nat_Nil [simp]: "bv_to_nat [] = 0"
by (simp add: bv_to_nat_def)
lemma bv_to_nat_helper [simp]: "bv_to_nat (b # bs) = bitval b * 2 ^ length bs + bv_to_nat bs"
proof -
let ?bv_to_nat' = "foldl (\<lambda>bn b. 2 * bn + bitval b)"
have helper: "\<And>base. ?bv_to_nat' base bs = base * 2 ^ length bs + ?bv_to_nat' 0 bs"
proof (induct bs)
case Nil
show ?case by simp
next
case (Cons x xs base)
show ?case
apply (simp only: foldl.simps)
apply (subst Cons [of "2 * base + bitval x"])
apply simp
apply (subst Cons [of "bitval x"])
apply (simp add: add_mult_distrib)
done
qed
show ?thesis by (simp add: bv_to_nat_def) (rule helper)
qed
lemma bv_to_nat0 [simp]: "bv_to_nat (\<zero>#bs) = bv_to_nat bs"
by simp
lemma bv_to_nat1 [simp]: "bv_to_nat (\<one>#bs) = 2 ^ length bs + bv_to_nat bs"
by simp
lemma bv_to_nat_upper_range: "bv_to_nat w < 2 ^ length w"
proof (induct w, simp_all)
fix b bs
assume "bv_to_nat bs < 2 ^ length bs"
show "bitval b * 2 ^ length bs + bv_to_nat bs < 2 * 2 ^ length bs"
proof (cases b, simp_all)
have "bv_to_nat bs < 2 ^ length bs" by fact
also have "... < 2 * 2 ^ length bs" by auto
finally show "bv_to_nat bs < 2 * 2 ^ length bs" by simp
next
have "bv_to_nat bs < 2 ^ length bs" by fact
hence "2 ^ length bs + bv_to_nat bs < 2 ^ length bs + 2 ^ length bs" by arith
also have "... = 2 * (2 ^ length bs)" by simp
finally show "bv_to_nat bs < 2 ^ length bs" by simp
qed
qed
lemma bv_extend_longer [simp]:
assumes wn: "n \<le> length w"
shows "bv_extend n b w = w"
by (simp add: bv_extend_def wn)
lemma bv_extend_shorter [simp]:
assumes wn: "length w < n"
shows "bv_extend n b w = bv_extend n b (b#w)"
proof -
from wn
have s: "n - Suc (length w) + 1 = n - length w"
by arith
have "bv_extend n b w = replicate (n - length w) b @ w"
by (simp add: bv_extend_def)
also have "... = replicate (n - Suc (length w) + 1) b @ w"
by (subst s) rule
also have "... = (replicate (n - Suc (length w)) b @ replicate 1 b) @ w"
by (subst replicate_add) rule
also have "... = replicate (n - Suc (length w)) b @ b # w"
by simp
also have "... = bv_extend n b (b#w)"
by (simp add: bv_extend_def)
finally show "bv_extend n b w = bv_extend n b (b#w)" .
qed
consts
rem_initial :: "bit => bit list => bit list"
primrec
"rem_initial b [] = []"
"rem_initial b (x#xs) = (if b = x then rem_initial b xs else x#xs)"
lemma rem_initial_length: "length (rem_initial b w) \<le> length w"
by (rule bit_list_induct [of _ w],simp_all (no_asm),safe,simp_all)
lemma rem_initial_equal:
assumes p: "length (rem_initial b w) = length w"
shows "rem_initial b w = w"
proof -
have "length (rem_initial b w) = length w --> rem_initial b w = w"
proof (induct w, simp_all, clarify)
fix xs
assume "length (rem_initial b xs) = length xs --> rem_initial b xs = xs"
assume f: "length (rem_initial b xs) = Suc (length xs)"
with rem_initial_length [of b xs]
show "rem_initial b xs = b#xs"
by auto
qed
from this and p show ?thesis ..
qed
lemma bv_extend_rem_initial: "bv_extend (length w) b (rem_initial b w) = w"
proof (induct w, simp_all, safe)
fix xs
assume ind: "bv_extend (length xs) b (rem_initial b xs) = xs"
from rem_initial_length [of b xs]
have [simp]: "Suc (length xs) - length (rem_initial b xs) =
1 + (length xs - length (rem_initial b xs))"
by arith
have "bv_extend (Suc (length xs)) b (rem_initial b xs) =
replicate (Suc (length xs) - length (rem_initial b xs)) b @ (rem_initial b xs)"
by (simp add: bv_extend_def)
also have "... =
replicate (1 + (length xs - length (rem_initial b xs))) b @ rem_initial b xs"
by simp
also have "... =
(replicate 1 b @ replicate (length xs - length (rem_initial b xs)) b) @ rem_initial b xs"
by (subst replicate_add) (rule refl)
also have "... = b # bv_extend (length xs) b (rem_initial b xs)"
by (auto simp add: bv_extend_def [symmetric])
also have "... = b # xs"
by (simp add: ind)
finally show "bv_extend (Suc (length xs)) b (rem_initial b xs) = b # xs" .
qed
lemma rem_initial_append1:
assumes "rem_initial b xs ~= []"
shows "rem_initial b (xs @ ys) = rem_initial b xs @ ys"
using assms by (induct xs) auto
lemma rem_initial_append2:
assumes "rem_initial b xs = []"
shows "rem_initial b (xs @ ys) = rem_initial b ys"
using assms by (induct xs) auto
definition
norm_unsigned :: "bit list => bit list" where
"norm_unsigned = rem_initial \<zero>"
lemma norm_unsigned_Nil [simp]: "norm_unsigned [] = []"
by (simp add: norm_unsigned_def)
lemma norm_unsigned_Cons0 [simp]: "norm_unsigned (\<zero>#bs) = norm_unsigned bs"
by (simp add: norm_unsigned_def)
lemma norm_unsigned_Cons1 [simp]: "norm_unsigned (\<one>#bs) = \<one>#bs"
by (simp add: norm_unsigned_def)
lemma norm_unsigned_idem [simp]: "norm_unsigned (norm_unsigned w) = norm_unsigned w"
by (rule bit_list_induct [of _ w],simp_all)
consts
nat_to_bv_helper :: "nat => bit list => bit list"
recdef nat_to_bv_helper "measure (\<lambda>n. n)"
"nat_to_bv_helper n = (%bs. (if n = 0 then bs
else nat_to_bv_helper (n div 2) ((if n mod 2 = 0 then \<zero> else \<one>)#bs)))"
definition
nat_to_bv :: "nat => bit list" where
"nat_to_bv n = nat_to_bv_helper n []"
lemma nat_to_bv0 [simp]: "nat_to_bv 0 = []"
by (simp add: nat_to_bv_def)
lemmas [simp del] = nat_to_bv_helper.simps
lemma n_div_2_cases:
assumes zero: "(n::nat) = 0 ==> R"
and div : "[| n div 2 < n ; 0 < n |] ==> R"
shows "R"
proof (cases "n = 0")
assume "n = 0"
thus R by (rule zero)
next
assume "n ~= 0"
hence "0 < n" by simp
hence "n div 2 < n" by arith
from this and `0 < n` show R by (rule div)
qed
lemma int_wf_ge_induct:
assumes ind : "!!i::int. (!!j. [| k \<le> j ; j < i |] ==> P j) ==> P i"
shows "P i"
proof (rule wf_induct_rule [OF wf_int_ge_less_than])
fix x
assume ih: "(\<And>y\<Colon>int. (y, x) \<in> int_ge_less_than k \<Longrightarrow> P y)"
thus "P x"
by (rule ind) (simp add: int_ge_less_than_def)
qed
lemma unfold_nat_to_bv_helper:
"nat_to_bv_helper b l = nat_to_bv_helper b [] @ l"
proof -
have "\<forall>l. nat_to_bv_helper b l = nat_to_bv_helper b [] @ l"
proof (induct b rule: less_induct)
fix n
assume ind: "!!j. j < n \<Longrightarrow> \<forall> l. nat_to_bv_helper j l = nat_to_bv_helper j [] @ l"
show "\<forall>l. nat_to_bv_helper n l = nat_to_bv_helper n [] @ l"
proof
fix l
show "nat_to_bv_helper n l = nat_to_bv_helper n [] @ l"
proof (cases "n < 0")
assume "n < 0"
thus ?thesis
by (simp add: nat_to_bv_helper.simps)
next
assume "~n < 0"
show ?thesis
proof (rule n_div_2_cases [of n])
assume [simp]: "n = 0"
show ?thesis
apply (simp only: nat_to_bv_helper.simps [of n])
apply simp
done
next
assume n2n: "n div 2 < n"
assume [simp]: "0 < n"
hence n20: "0 \<le> n div 2"
by arith
from ind [of "n div 2"] and n2n n20
have ind': "\<forall>l. nat_to_bv_helper (n div 2) l = nat_to_bv_helper (n div 2) [] @ l"
by blast
show ?thesis
apply (simp only: nat_to_bv_helper.simps [of n])
apply (cases "n=0")
apply simp
apply (simp only: if_False)
apply simp
apply (subst spec [OF ind',of "\<zero>#l"])
apply (subst spec [OF ind',of "\<one>#l"])
apply (subst spec [OF ind',of "[\<one>]"])
apply (subst spec [OF ind',of "[\<zero>]"])
apply simp
done
qed
qed
qed
qed
thus ?thesis ..
qed
lemma nat_to_bv_non0 [simp]: "n\<noteq>0 ==> nat_to_bv n = nat_to_bv (n div 2) @ [if n mod 2 = 0 then \<zero> else \<one>]"
proof -
assume [simp]: "n\<noteq>0"
show ?thesis
apply (subst nat_to_bv_def [of n])
apply (simp only: nat_to_bv_helper.simps [of n])
apply (subst unfold_nat_to_bv_helper)
using prems
apply (simp)
apply (subst nat_to_bv_def [of "n div 2"])
apply auto
done
qed
lemma bv_to_nat_dist_append:
"bv_to_nat (l1 @ l2) = bv_to_nat l1 * 2 ^ length l2 + bv_to_nat l2"
proof -
have "\<forall>l2. bv_to_nat (l1 @ l2) = bv_to_nat l1 * 2 ^ length l2 + bv_to_nat l2"
proof (induct l1,simp_all)
fix x xs
assume ind: "\<forall>l2. bv_to_nat (xs @ l2) = bv_to_nat xs * 2 ^ length l2 + bv_to_nat l2"
show "\<forall>l2. bv_to_nat xs * 2 ^ length l2 + bitval x * 2 ^ (length xs + length l2) = (bitval x * 2 ^ length xs + bv_to_nat xs) * 2 ^ length l2"
proof
fix l2
show "bv_to_nat xs * 2 ^ length l2 + bitval x * 2 ^ (length xs + length l2) = (bitval x * 2 ^ length xs + bv_to_nat xs) * 2 ^ length l2"
proof -
have "(2::nat) ^ (length xs + length l2) = 2 ^ length xs * 2 ^ length l2"
by (induct "length xs",simp_all)
hence "bitval x * 2 ^ (length xs + length l2) + bv_to_nat xs * 2 ^ length l2 =
bitval x * 2 ^ length xs * 2 ^ length l2 + bv_to_nat xs * 2 ^ length l2"
by simp
also have "... = (bitval x * 2 ^ length xs + bv_to_nat xs) * 2 ^ length l2"
by (simp add: ring_distribs)
finally show ?thesis by simp
qed
qed
qed
thus ?thesis ..
qed
lemma bv_nat_bv [simp]: "bv_to_nat (nat_to_bv n) = n"
proof (induct n rule: less_induct)
fix n
assume ind: "!!j. j < n \<Longrightarrow> bv_to_nat (nat_to_bv j) = j"
show "bv_to_nat (nat_to_bv n) = n"
proof (rule n_div_2_cases [of n])
assume "n = 0" then show ?thesis by simp
next
assume nn: "n div 2 < n"
assume n0: "0 < n"
from ind and nn
have ind': "bv_to_nat (nat_to_bv (n div 2)) = n div 2" by blast
from n0 have n0': "n \<noteq> 0" by simp
show ?thesis
apply (subst nat_to_bv_def)
apply (simp only: nat_to_bv_helper.simps [of n])
apply (simp only: n0' if_False)
apply (subst unfold_nat_to_bv_helper)
apply (subst bv_to_nat_dist_append)
apply (fold nat_to_bv_def)
apply (simp add: ind' split del: split_if)
apply (cases "n mod 2 = 0")
proof (simp_all)
assume "n mod 2 = 0"
with mod_div_equality [of n 2]
show "n div 2 * 2 = n" by simp
next
assume "n mod 2 = Suc 0"
with mod_div_equality [of n 2]
show "Suc (n div 2 * 2) = n" by arith
qed
qed
qed
lemma bv_to_nat_type [simp]: "bv_to_nat (norm_unsigned w) = bv_to_nat w"
by (rule bit_list_induct) simp_all
lemma length_norm_unsigned_le [simp]: "length (norm_unsigned w) \<le> length w"
by (rule bit_list_induct) simp_all
lemma bv_to_nat_rew_msb: "bv_msb w = \<one> ==> bv_to_nat w = 2 ^ (length w - 1) + bv_to_nat (tl w)"
by (rule bit_list_cases [of w]) simp_all
lemma norm_unsigned_result: "norm_unsigned xs = [] \<or> bv_msb (norm_unsigned xs) = \<one>"
proof (rule length_induct [of _ xs])
fix xs :: "bit list"
assume ind: "\<forall>ys. length ys < length xs --> norm_unsigned ys = [] \<or> bv_msb (norm_unsigned ys) = \<one>"
show "norm_unsigned xs = [] \<or> bv_msb (norm_unsigned xs) = \<one>"
proof (rule bit_list_cases [of xs],simp_all)
fix bs
assume [simp]: "xs = \<zero>#bs"
from ind
have "length bs < length xs --> norm_unsigned bs = [] \<or> bv_msb (norm_unsigned bs) = \<one>" ..
thus "norm_unsigned bs = [] \<or> bv_msb (norm_unsigned bs) = \<one>" by simp
qed
qed
lemma norm_empty_bv_to_nat_zero:
assumes nw: "norm_unsigned w = []"
shows "bv_to_nat w = 0"
proof -
have "bv_to_nat w = bv_to_nat (norm_unsigned w)" by simp
also have "... = bv_to_nat []" by (subst nw) (rule refl)
also have "... = 0" by simp
finally show ?thesis .
qed
lemma bv_to_nat_lower_limit:
assumes w0: "0 < bv_to_nat w"
shows "2 ^ (length (norm_unsigned w) - 1) \<le> bv_to_nat w"
proof -
from w0 and norm_unsigned_result [of w]
have msbw: "bv_msb (norm_unsigned w) = \<one>"
by (auto simp add: norm_empty_bv_to_nat_zero)
have "2 ^ (length (norm_unsigned w) - 1) \<le> bv_to_nat (norm_unsigned w)"
by (subst bv_to_nat_rew_msb [OF msbw],simp)
thus ?thesis by simp
qed
lemmas [simp del] = nat_to_bv_non0
lemma norm_unsigned_length [intro!]: "length (norm_unsigned w) \<le> length w"
by (subst norm_unsigned_def,rule rem_initial_length)
lemma norm_unsigned_equal:
"length (norm_unsigned w) = length w ==> norm_unsigned w = w"
by (simp add: norm_unsigned_def,rule rem_initial_equal)
lemma bv_extend_norm_unsigned: "bv_extend (length w) \<zero> (norm_unsigned w) = w"
by (simp add: norm_unsigned_def,rule bv_extend_rem_initial)
lemma norm_unsigned_append1 [simp]:
"norm_unsigned xs \<noteq> [] ==> norm_unsigned (xs @ ys) = norm_unsigned xs @ ys"
by (simp add: norm_unsigned_def,rule rem_initial_append1)
lemma norm_unsigned_append2 [simp]:
"norm_unsigned xs = [] ==> norm_unsigned (xs @ ys) = norm_unsigned ys"
by (simp add: norm_unsigned_def,rule rem_initial_append2)
lemma bv_to_nat_zero_imp_empty:
"bv_to_nat w = 0 \<Longrightarrow> norm_unsigned w = []"
by (atomize (full), induct w rule: bit_list_induct) simp_all
lemma bv_to_nat_nzero_imp_nempty:
"bv_to_nat w \<noteq> 0 \<Longrightarrow> norm_unsigned w \<noteq> []"
by (induct w rule: bit_list_induct) simp_all
lemma nat_helper1:
assumes ass: "nat_to_bv (bv_to_nat w) = norm_unsigned w"
shows "nat_to_bv (2 * bv_to_nat w + bitval x) = norm_unsigned (w @ [x])"
proof (cases x)
assume [simp]: "x = \<one>"
show ?thesis
apply (simp add: nat_to_bv_non0)
apply safe
proof -
fix q
assume "Suc (2 * bv_to_nat w) = 2 * q"
hence orig: "(2 * bv_to_nat w + 1) mod 2 = 2 * q mod 2" (is "?lhs = ?rhs")
by simp
have "?lhs = (1 + 2 * bv_to_nat w) mod 2"
by (simp add: add_commute)
also have "... = 1"
by (subst mod_add1_eq) simp
finally have eq1: "?lhs = 1" .
have "?rhs = 0" by simp
with orig and eq1
show "nat_to_bv (Suc (2 * bv_to_nat w) div 2) @ [\<zero>] = norm_unsigned (w @ [\<one>])"
by simp
next
have "nat_to_bv (Suc (2 * bv_to_nat w) div 2) @ [\<one>] =
nat_to_bv ((1 + 2 * bv_to_nat w) div 2) @ [\<one>]"
by (simp add: add_commute)
also have "... = nat_to_bv (bv_to_nat w) @ [\<one>]"
by (subst div_add1_eq) simp
also have "... = norm_unsigned w @ [\<one>]"
by (subst ass) (rule refl)
also have "... = norm_unsigned (w @ [\<one>])"
by (cases "norm_unsigned w") simp_all
finally show "nat_to_bv (Suc (2 * bv_to_nat w) div 2) @ [\<one>] = norm_unsigned (w @ [\<one>])" .
qed
next
assume [simp]: "x = \<zero>"
show ?thesis
proof (cases "bv_to_nat w = 0")
assume "bv_to_nat w = 0"
thus ?thesis
by (simp add: bv_to_nat_zero_imp_empty)
next
assume "bv_to_nat w \<noteq> 0"
thus ?thesis
apply simp
apply (subst nat_to_bv_non0)
apply simp
apply auto
apply (subst ass)
apply (cases "norm_unsigned w")
apply (simp_all add: norm_empty_bv_to_nat_zero)
done
qed
qed
lemma nat_helper2: "nat_to_bv (2 ^ length xs + bv_to_nat xs) = \<one> # xs"
proof -
have "\<forall>xs. nat_to_bv (2 ^ length (rev xs) + bv_to_nat (rev xs)) = \<one> # (rev xs)" (is "\<forall>xs. ?P xs")
proof
fix xs
show "?P xs"
proof (rule length_induct [of _ xs])
fix xs :: "bit list"
assume ind: "\<forall>ys. length ys < length xs --> ?P ys"
show "?P xs"
proof (cases xs)
assume "xs = []"
then show ?thesis by (simp add: nat_to_bv_non0)
next
fix y ys
assume [simp]: "xs = y # ys"
show ?thesis
apply simp
apply (subst bv_to_nat_dist_append)
apply simp
proof -
have "nat_to_bv (2 * 2 ^ length ys + (bv_to_nat (rev ys) * 2 + bitval y)) =
nat_to_bv (2 * (2 ^ length ys + bv_to_nat (rev ys)) + bitval y)"
by (simp add: add_ac mult_ac)
also have "... = nat_to_bv (2 * (bv_to_nat (\<one>#rev ys)) + bitval y)"
by simp
also have "... = norm_unsigned (\<one>#rev ys) @ [y]"
proof -
from ind
have "nat_to_bv (2 ^ length (rev ys) + bv_to_nat (rev ys)) = \<one> # rev ys"
by auto
hence [simp]: "nat_to_bv (2 ^ length ys + bv_to_nat (rev ys)) = \<one> # rev ys"
by simp
show ?thesis
apply (subst nat_helper1)
apply simp_all
done
qed
also have "... = (\<one>#rev ys) @ [y]"
by simp
also have "... = \<one> # rev ys @ [y]"
by simp
finally show "nat_to_bv (2 * 2 ^ length ys + (bv_to_nat (rev ys) * 2 + bitval y)) =
\<one> # rev ys @ [y]" .
qed
qed
qed
qed
hence "nat_to_bv (2 ^ length (rev (rev xs)) + bv_to_nat (rev (rev xs))) =
\<one> # rev (rev xs)" ..
thus ?thesis by simp
qed
lemma nat_bv_nat [simp]: "nat_to_bv (bv_to_nat w) = norm_unsigned w"
proof (rule bit_list_induct [of _ w],simp_all)
fix xs
assume "nat_to_bv (bv_to_nat xs) = norm_unsigned xs"
have "bv_to_nat xs = bv_to_nat (norm_unsigned xs)" by simp
have "bv_to_nat xs < 2 ^ length xs"
by (rule bv_to_nat_upper_range)
show "nat_to_bv (2 ^ length xs + bv_to_nat xs) = \<one> # xs"
by (rule nat_helper2)
qed
lemma bv_to_nat_qinj:
assumes one: "bv_to_nat xs = bv_to_nat ys"
and len: "length xs = length ys"
shows "xs = ys"
proof -
from one
have "nat_to_bv (bv_to_nat xs) = nat_to_bv (bv_to_nat ys)"
by simp
hence xsys: "norm_unsigned xs = norm_unsigned ys"
by simp
have "xs = bv_extend (length xs) \<zero> (norm_unsigned xs)"
by (simp add: bv_extend_norm_unsigned)
also have "... = bv_extend (length ys) \<zero> (norm_unsigned ys)"
by (simp add: xsys len)
also have "... = ys"
by (simp add: bv_extend_norm_unsigned)
finally show ?thesis .
qed
lemma norm_unsigned_nat_to_bv [simp]:
"norm_unsigned (nat_to_bv n) = nat_to_bv n"
proof -
have "norm_unsigned (nat_to_bv n) = nat_to_bv (bv_to_nat (norm_unsigned (nat_to_bv n)))"
by (subst nat_bv_nat) simp
also have "... = nat_to_bv n" by simp
finally show ?thesis .
qed
lemma length_nat_to_bv_upper_limit:
assumes nk: "n \<le> 2 ^ k - 1"
shows "length (nat_to_bv n) \<le> k"
proof (cases "n = 0")
case True
thus ?thesis
by (simp add: nat_to_bv_def nat_to_bv_helper.simps)
next
case False
hence n0: "0 < n" by simp
show ?thesis
proof (rule ccontr)
assume "~ length (nat_to_bv n) \<le> k"
hence "k < length (nat_to_bv n)" by simp
hence "k \<le> length (nat_to_bv n) - 1" by arith
hence "(2::nat) ^ k \<le> 2 ^ (length (nat_to_bv n) - 1)" by simp
also have "... = 2 ^ (length (norm_unsigned (nat_to_bv n)) - 1)" by simp
also have "... \<le> bv_to_nat (nat_to_bv n)"
by (rule bv_to_nat_lower_limit) (simp add: n0)
also have "... = n" by simp
finally have "2 ^ k \<le> n" .
with n0 have "2 ^ k - 1 < n" by arith
with nk show False by simp
qed
qed
lemma length_nat_to_bv_lower_limit:
assumes nk: "2 ^ k \<le> n"
shows "k < length (nat_to_bv n)"
proof (rule ccontr)
assume "~ k < length (nat_to_bv n)"
hence lnk: "length (nat_to_bv n) \<le> k" by simp
have "n = bv_to_nat (nat_to_bv n)" by simp
also have "... < 2 ^ length (nat_to_bv n)"
by (rule bv_to_nat_upper_range)
also from lnk have "... \<le> 2 ^ k" by simp
finally have "n < 2 ^ k" .
with nk show False by simp
qed
subsection {* Unsigned Arithmetic Operations *}
definition
bv_add :: "[bit list, bit list ] => bit list" where
"bv_add w1 w2 = nat_to_bv (bv_to_nat w1 + bv_to_nat w2)"
lemma bv_add_type1 [simp]: "bv_add (norm_unsigned w1) w2 = bv_add w1 w2"
by (simp add: bv_add_def)
lemma bv_add_type2 [simp]: "bv_add w1 (norm_unsigned w2) = bv_add w1 w2"
by (simp add: bv_add_def)
lemma bv_add_returntype [simp]: "norm_unsigned (bv_add w1 w2) = bv_add w1 w2"
by (simp add: bv_add_def)
lemma bv_add_length: "length (bv_add w1 w2) \<le> Suc (max (length w1) (length w2))"
proof (unfold bv_add_def,rule length_nat_to_bv_upper_limit)
from bv_to_nat_upper_range [of w1] and bv_to_nat_upper_range [of w2]
have "bv_to_nat w1 + bv_to_nat w2 \<le> (2 ^ length w1 - 1) + (2 ^ length w2 - 1)"
by arith
also have "... \<le>
max (2 ^ length w1 - 1) (2 ^ length w2 - 1) + max (2 ^ length w1 - 1) (2 ^ length w2 - 1)"
by (rule add_mono,safe intro!: le_maxI1 le_maxI2)
also have "... = 2 * max (2 ^ length w1 - 1) (2 ^ length w2 - 1)" by simp
also have "... \<le> 2 ^ Suc (max (length w1) (length w2)) - 2"
proof (cases "length w1 \<le> length w2")
assume w1w2: "length w1 \<le> length w2"
hence "(2::nat) ^ length w1 \<le> 2 ^ length w2" by simp
hence "(2::nat) ^ length w1 - 1 \<le> 2 ^ length w2 - 1" by arith
with w1w2 show ?thesis
by (simp add: diff_mult_distrib2 split: split_max)
next
assume [simp]: "~ (length w1 \<le> length w2)"
have "~ ((2::nat) ^ length w1 - 1 \<le> 2 ^ length w2 - 1)"
proof
assume "(2::nat) ^ length w1 - 1 \<le> 2 ^ length w2 - 1"
hence "((2::nat) ^ length w1 - 1) + 1 \<le> (2 ^ length w2 - 1) + 1"
by (rule add_right_mono)
hence "(2::nat) ^ length w1 \<le> 2 ^ length w2" by simp
hence "length w1 \<le> length w2" by simp
thus False by simp
qed
thus ?thesis
by (simp add: diff_mult_distrib2 split: split_max)
qed
finally show "bv_to_nat w1 + bv_to_nat w2 \<le> 2 ^ Suc (max (length w1) (length w2)) - 1"
by arith
qed
definition
bv_mult :: "[bit list, bit list ] => bit list" where
"bv_mult w1 w2 = nat_to_bv (bv_to_nat w1 * bv_to_nat w2)"
lemma bv_mult_type1 [simp]: "bv_mult (norm_unsigned w1) w2 = bv_mult w1 w2"
by (simp add: bv_mult_def)
lemma bv_mult_type2 [simp]: "bv_mult w1 (norm_unsigned w2) = bv_mult w1 w2"
by (simp add: bv_mult_def)
lemma bv_mult_returntype [simp]: "norm_unsigned (bv_mult w1 w2) = bv_mult w1 w2"
by (simp add: bv_mult_def)
lemma bv_mult_length: "length (bv_mult w1 w2) \<le> length w1 + length w2"
proof (unfold bv_mult_def,rule length_nat_to_bv_upper_limit)
from bv_to_nat_upper_range [of w1] and bv_to_nat_upper_range [of w2]
have h: "bv_to_nat w1 \<le> 2 ^ length w1 - 1 \<and> bv_to_nat w2 \<le> 2 ^ length w2 - 1"
by arith
have "bv_to_nat w1 * bv_to_nat w2 \<le> (2 ^ length w1 - 1) * (2 ^ length w2 - 1)"
apply (cut_tac h)
apply (rule mult_mono)
apply auto
done
also have "... < 2 ^ length w1 * 2 ^ length w2"
by (rule mult_strict_mono,auto)
also have "... = 2 ^ (length w1 + length w2)"
by (simp add: power_add)
finally show "bv_to_nat w1 * bv_to_nat w2 \<le> 2 ^ (length w1 + length w2) - 1"
by arith
qed
subsection {* Signed Vectors *}
consts
norm_signed :: "bit list => bit list"
primrec
norm_signed_Nil: "norm_signed [] = []"
norm_signed_Cons: "norm_signed (b#bs) =
(case b of
\<zero> => if norm_unsigned bs = [] then [] else b#norm_unsigned bs
| \<one> => b#rem_initial b bs)"
lemma norm_signed0 [simp]: "norm_signed [\<zero>] = []"
by simp
lemma norm_signed1 [simp]: "norm_signed [\<one>] = [\<one>]"
by simp
lemma norm_signed01 [simp]: "norm_signed (\<zero>#\<one>#xs) = \<zero>#\<one>#xs"
by simp
lemma norm_signed00 [simp]: "norm_signed (\<zero>#\<zero>#xs) = norm_signed (\<zero>#xs)"
by simp
lemma norm_signed10 [simp]: "norm_signed (\<one>#\<zero>#xs) = \<one>#\<zero>#xs"
by simp
lemma norm_signed11 [simp]: "norm_signed (\<one>#\<one>#xs) = norm_signed (\<one>#xs)"
by simp
lemmas [simp del] = norm_signed_Cons
definition
int_to_bv :: "int => bit list" where
"int_to_bv n = (if 0 \<le> n
then norm_signed (\<zero>#nat_to_bv (nat n))
else norm_signed (bv_not (\<zero>#nat_to_bv (nat (-n- 1)))))"
lemma int_to_bv_ge0 [simp]: "0 \<le> n ==> int_to_bv n = norm_signed (\<zero> # nat_to_bv (nat n))"
by (simp add: int_to_bv_def)
lemma int_to_bv_lt0 [simp]:
"n < 0 ==> int_to_bv n = norm_signed (bv_not (\<zero>#nat_to_bv (nat (-n- 1))))"
by (simp add: int_to_bv_def)
lemma norm_signed_idem [simp]: "norm_signed (norm_signed w) = norm_signed w"
proof (rule bit_list_induct [of _ w], simp_all)
fix xs
assume eq: "norm_signed (norm_signed xs) = norm_signed xs"
show "norm_signed (norm_signed (\<zero>#xs)) = norm_signed (\<zero>#xs)"
proof (rule bit_list_cases [of xs],simp_all)
fix ys
assume "xs = \<zero>#ys"
from this [symmetric] and eq
show "norm_signed (norm_signed (\<zero>#ys)) = norm_signed (\<zero>#ys)"
by simp
qed
next
fix xs
assume eq: "norm_signed (norm_signed xs) = norm_signed xs"
show "norm_signed (norm_signed (\<one>#xs)) = norm_signed (\<one>#xs)"
proof (rule bit_list_cases [of xs],simp_all)
fix ys
assume "xs = \<one>#ys"
from this [symmetric] and eq
show "norm_signed (norm_signed (\<one>#ys)) = norm_signed (\<one>#ys)"
by simp
qed
qed
definition
bv_to_int :: "bit list => int" where
"bv_to_int w =
(case bv_msb w of \<zero> => int (bv_to_nat w)
| \<one> => - int (bv_to_nat (bv_not w) + 1))"
lemma bv_to_int_Nil [simp]: "bv_to_int [] = 0"
by (simp add: bv_to_int_def)
lemma bv_to_int_Cons0 [simp]: "bv_to_int (\<zero>#bs) = int (bv_to_nat bs)"
by (simp add: bv_to_int_def)
lemma bv_to_int_Cons1 [simp]: "bv_to_int (\<one>#bs) = - int (bv_to_nat (bv_not bs) + 1)"
by (simp add: bv_to_int_def)
lemma bv_to_int_type [simp]: "bv_to_int (norm_signed w) = bv_to_int w"
proof (rule bit_list_induct [of _ w], simp_all)
fix xs
assume ind: "bv_to_int (norm_signed xs) = bv_to_int xs"
show "bv_to_int (norm_signed (\<zero>#xs)) = int (bv_to_nat xs)"
proof (rule bit_list_cases [of xs], simp_all)
fix ys
assume [simp]: "xs = \<zero>#ys"
from ind
show "bv_to_int (norm_signed (\<zero>#ys)) = int (bv_to_nat ys)"
by simp
qed
next
fix xs
assume ind: "bv_to_int (norm_signed xs) = bv_to_int xs"
show "bv_to_int (norm_signed (\<one>#xs)) = -1 - int (bv_to_nat (bv_not xs))"
proof (rule bit_list_cases [of xs], simp_all)
fix ys
assume [simp]: "xs = \<one>#ys"
from ind
show "bv_to_int (norm_signed (\<one>#ys)) = -1 - int (bv_to_nat (bv_not ys))"
by simp
qed
qed
lemma bv_to_int_upper_range: "bv_to_int w < 2 ^ (length w - 1)"
proof (rule bit_list_cases [of w],simp_all)
fix bs
from bv_to_nat_upper_range
show "int (bv_to_nat bs) < 2 ^ length bs"
by (simp add: int_nat_two_exp)
next
fix bs
have "-1 - int (bv_to_nat (bv_not bs)) \<le> 0" by simp
also have "... < 2 ^ length bs" by (induct bs) simp_all
finally show "-1 - int (bv_to_nat (bv_not bs)) < 2 ^ length bs" .
qed
lemma bv_to_int_lower_range: "- (2 ^ (length w - 1)) \<le> bv_to_int w"
proof (rule bit_list_cases [of w],simp_all)
fix bs :: "bit list"
have "- (2 ^ length bs) \<le> (0::int)" by (induct bs) simp_all
also have "... \<le> int (bv_to_nat bs)" by simp
finally show "- (2 ^ length bs) \<le> int (bv_to_nat bs)" .
next
fix bs
from bv_to_nat_upper_range [of "bv_not bs"]
show "- (2 ^ length bs) \<le> -1 - int (bv_to_nat (bv_not bs))"
by (simp add: int_nat_two_exp)
qed
lemma int_bv_int [simp]: "int_to_bv (bv_to_int w) = norm_signed w"
proof (rule bit_list_cases [of w],simp)
fix xs
assume [simp]: "w = \<zero>#xs"
show ?thesis
apply simp
apply (subst norm_signed_Cons [of "\<zero>" "xs"])
apply simp
using norm_unsigned_result [of xs]
apply safe
apply (rule bit_list_cases [of "norm_unsigned xs"])
apply simp_all
done
next
fix xs
assume [simp]: "w = \<one>#xs"
show ?thesis
apply (simp del: int_to_bv_lt0)
apply (rule bit_list_induct [of _ xs])
apply simp
apply (subst int_to_bv_lt0)
apply (subgoal_tac "- int (bv_to_nat (bv_not (\<zero> # bs))) + -1 < 0 + 0")
apply simp
apply (rule add_le_less_mono)
apply simp
apply simp
apply (simp del: bv_to_nat1 bv_to_nat_helper)
apply simp
done
qed
lemma bv_int_bv [simp]: "bv_to_int (int_to_bv i) = i"
by (cases "0 \<le> i") simp_all
lemma bv_msb_norm [simp]: "bv_msb (norm_signed w) = bv_msb w"
by (rule bit_list_cases [of w]) (simp_all add: norm_signed_Cons)
lemma norm_signed_length: "length (norm_signed w) \<le> length w"
apply (cases w, simp_all)
apply (subst norm_signed_Cons)
apply (case_tac a, simp_all)
apply (rule rem_initial_length)
done
lemma norm_signed_equal: "length (norm_signed w) = length w ==> norm_signed w = w"
proof (rule bit_list_cases [of w], simp_all)
fix xs
assume "length (norm_signed (\<zero>#xs)) = Suc (length xs)"
thus "norm_signed (\<zero>#xs) = \<zero>#xs"
apply (simp add: norm_signed_Cons)
apply safe
apply simp_all
apply (rule norm_unsigned_equal)
apply assumption
done
next
fix xs
assume "length (norm_signed (\<one>#xs)) = Suc (length xs)"
thus "norm_signed (\<one>#xs) = \<one>#xs"
apply (simp add: norm_signed_Cons)
apply (rule rem_initial_equal)
apply assumption
done
qed
lemma bv_extend_norm_signed: "bv_msb w = b ==> bv_extend (length w) b (norm_signed w) = w"
proof (rule bit_list_cases [of w],simp_all)
fix xs
show "bv_extend (Suc (length xs)) \<zero> (norm_signed (\<zero>#xs)) = \<zero>#xs"
proof (simp add: norm_signed_list_def,auto)
assume "norm_unsigned xs = []"
hence xx: "rem_initial \<zero> xs = []"
by (simp add: norm_unsigned_def)
have "bv_extend (Suc (length xs)) \<zero> (\<zero>#rem_initial \<zero> xs) = \<zero>#xs"
apply (simp add: bv_extend_def replicate_app_Cons_same)
apply (fold bv_extend_def)
apply (rule bv_extend_rem_initial)
done
thus "bv_extend (Suc (length xs)) \<zero> [\<zero>] = \<zero>#xs"
by (simp add: xx)
next
show "bv_extend (Suc (length xs)) \<zero> (\<zero>#norm_unsigned xs) = \<zero>#xs"
apply (simp add: norm_unsigned_def)
apply (simp add: bv_extend_def replicate_app_Cons_same)
apply (fold bv_extend_def)
apply (rule bv_extend_rem_initial)
done
qed
next
fix xs
show "bv_extend (Suc (length xs)) \<one> (norm_signed (\<one>#xs)) = \<one>#xs"
apply (simp add: norm_signed_Cons)
apply (simp add: bv_extend_def replicate_app_Cons_same)
apply (fold bv_extend_def)
apply (rule bv_extend_rem_initial)
done
qed
lemma bv_to_int_qinj:
assumes one: "bv_to_int xs = bv_to_int ys"
and len: "length xs = length ys"
shows "xs = ys"
proof -
from one
have "int_to_bv (bv_to_int xs) = int_to_bv (bv_to_int ys)" by simp
hence xsys: "norm_signed xs = norm_signed ys" by simp
hence xsys': "bv_msb xs = bv_msb ys"
proof -
have "bv_msb xs = bv_msb (norm_signed xs)" by simp
also have "... = bv_msb (norm_signed ys)" by (simp add: xsys)
also have "... = bv_msb ys" by simp
finally show ?thesis .
qed
have "xs = bv_extend (length xs) (bv_msb xs) (norm_signed xs)"
by (simp add: bv_extend_norm_signed)
also have "... = bv_extend (length ys) (bv_msb ys) (norm_signed ys)"
by (simp add: xsys xsys' len)
also have "... = ys"
by (simp add: bv_extend_norm_signed)
finally show ?thesis .
qed
lemma int_to_bv_returntype [simp]: "norm_signed (int_to_bv w) = int_to_bv w"
by (simp add: int_to_bv_def)
lemma bv_to_int_msb0: "0 \<le> bv_to_int w1 ==> bv_msb w1 = \<zero>"
by (rule bit_list_cases,simp_all)
lemma bv_to_int_msb1: "bv_to_int w1 < 0 ==> bv_msb w1 = \<one>"
by (rule bit_list_cases,simp_all)
lemma bv_to_int_lower_limit_gt0:
assumes w0: "0 < bv_to_int w"
shows "2 ^ (length (norm_signed w) - 2) \<le> bv_to_int w"
proof -
from w0
have "0 \<le> bv_to_int w" by simp
hence [simp]: "bv_msb w = \<zero>" by (rule bv_to_int_msb0)
have "2 ^ (length (norm_signed w) - 2) \<le> bv_to_int (norm_signed w)"
proof (rule bit_list_cases [of w])
assume "w = []"
with w0 show ?thesis by simp
next
fix w'
assume weq: "w = \<zero> # w'"
thus ?thesis
proof (simp add: norm_signed_Cons,safe)
assume "norm_unsigned w' = []"
with weq and w0 show False
by (simp add: norm_empty_bv_to_nat_zero)
next
assume w'0: "norm_unsigned w' \<noteq> []"
have "0 < bv_to_nat w'"
proof (rule ccontr)
assume "~ (0 < bv_to_nat w')"
hence "bv_to_nat w' = 0"
by arith
hence "norm_unsigned w' = []"
by (simp add: bv_to_nat_zero_imp_empty)
with w'0
show False by simp
qed
with bv_to_nat_lower_limit [of w']
show "2 ^ (length (norm_unsigned w') - Suc 0) \<le> int (bv_to_nat w')"
by (simp add: int_nat_two_exp)
qed
next
fix w'
assume "w = \<one> # w'"
from w0 have "bv_msb w = \<zero>" by simp
with prems show ?thesis by simp
qed
also have "... = bv_to_int w" by simp
finally show ?thesis .
qed
lemma norm_signed_result: "norm_signed w = [] \<or> norm_signed w = [\<one>] \<or> bv_msb (norm_signed w) \<noteq> bv_msb (tl (norm_signed w))"
apply (rule bit_list_cases [of w],simp_all)
apply (case_tac "bs",simp_all)
apply (case_tac "a",simp_all)
apply (simp add: norm_signed_Cons)
apply safe
apply simp
proof -
fix l
assume msb: "\<zero> = bv_msb (norm_unsigned l)"
assume "norm_unsigned l \<noteq> []"
with norm_unsigned_result [of l]
have "bv_msb (norm_unsigned l) = \<one>" by simp
with msb show False by simp
next
fix xs
assume p: "\<one> = bv_msb (tl (norm_signed (\<one> # xs)))"
have "\<one> \<noteq> bv_msb (tl (norm_signed (\<one> # xs)))"
by (rule bit_list_induct [of _ xs],simp_all)
with p show False by simp
qed
lemma bv_to_int_upper_limit_lem1:
assumes w0: "bv_to_int w < -1"
shows "bv_to_int w < - (2 ^ (length (norm_signed w) - 2))"
proof -
from w0
have "bv_to_int w < 0" by simp
hence msbw [simp]: "bv_msb w = \<one>"
by (rule bv_to_int_msb1)
have "bv_to_int w = bv_to_int (norm_signed w)" by simp
also from norm_signed_result [of w]
have "... < - (2 ^ (length (norm_signed w) - 2))"
proof safe
assume "norm_signed w = []"
hence "bv_to_int (norm_signed w) = 0" by simp
with w0 show ?thesis by simp
next
assume "norm_signed w = [\<one>]"
hence "bv_to_int (norm_signed w) = -1" by simp
with w0 show ?thesis by simp
next
assume "bv_msb (norm_signed w) \<noteq> bv_msb (tl (norm_signed w))"
hence msb_tl: "\<one> \<noteq> bv_msb (tl (norm_signed w))" by simp
show "bv_to_int (norm_signed w) < - (2 ^ (length (norm_signed w) - 2))"
proof (rule bit_list_cases [of "norm_signed w"])
assume "norm_signed w = []"
hence "bv_to_int (norm_signed w) = 0" by simp
with w0 show ?thesis by simp
next
fix w'
assume nw: "norm_signed w = \<zero> # w'"
from msbw have "bv_msb (norm_signed w) = \<one>" by simp
with nw show ?thesis by simp
next
fix w'
assume weq: "norm_signed w = \<one> # w'"
show ?thesis
proof (rule bit_list_cases [of w'])
assume w'eq: "w' = []"
from w0 have "bv_to_int (norm_signed w) < -1" by simp
with w'eq and weq show ?thesis by simp
next
fix w''
assume w'eq: "w' = \<zero> # w''"
show ?thesis
apply (simp add: weq w'eq)
apply (subgoal_tac "- int (bv_to_nat (bv_not w'')) + -1 < 0 + 0")
apply (simp add: int_nat_two_exp)
apply (rule add_le_less_mono)
apply simp_all
done
next
fix w''
assume w'eq: "w' = \<one> # w''"
with weq and msb_tl show ?thesis by simp
qed
qed
qed
finally show ?thesis .
qed
lemma length_int_to_bv_upper_limit_gt0:
assumes w0: "0 < i"
and wk: "i \<le> 2 ^ (k - 1) - 1"
shows "length (int_to_bv i) \<le> k"
proof (rule ccontr)
from w0 wk
have k1: "1 < k"
by (cases "k - 1",simp_all)
assume "~ length (int_to_bv i) \<le> k"
hence "k < length (int_to_bv i)" by simp
hence "k \<le> length (int_to_bv i) - 1" by arith
hence a: "k - 1 \<le> length (int_to_bv i) - 2" by arith
hence "(2::int) ^ (k - 1) \<le> 2 ^ (length (int_to_bv i) - 2)" by simp
also have "... \<le> i"
proof -
have "2 ^ (length (norm_signed (int_to_bv i)) - 2) \<le> bv_to_int (int_to_bv i)"
proof (rule bv_to_int_lower_limit_gt0)
from w0 show "0 < bv_to_int (int_to_bv i)" by simp
qed
thus ?thesis by simp
qed
finally have "2 ^ (k - 1) \<le> i" .
with wk show False by simp
qed
lemma pos_length_pos:
assumes i0: "0 < bv_to_int w"
shows "0 < length w"
proof -
from norm_signed_result [of w]
have "0 < length (norm_signed w)"
proof (auto)
assume ii: "norm_signed w = []"
have "bv_to_int (norm_signed w) = 0" by (subst ii) simp
hence "bv_to_int w = 0" by simp
with i0 show False by simp
next
assume ii: "norm_signed w = []"
assume jj: "bv_msb w \<noteq> \<zero>"
have "\<zero> = bv_msb (norm_signed w)"
by (subst ii) simp
also have "... \<noteq> \<zero>"
by (simp add: jj)
finally show False by simp
qed
also have "... \<le> length w"
by (rule norm_signed_length)
finally show ?thesis .
qed
lemma neg_length_pos:
assumes i0: "bv_to_int w < -1"
shows "0 < length w"
proof -
from norm_signed_result [of w]
have "0 < length (norm_signed w)"
proof (auto)
assume ii: "norm_signed w = []"
have "bv_to_int (norm_signed w) = 0"
by (subst ii) simp
hence "bv_to_int w = 0" by simp
with i0 show False by simp
next
assume ii: "norm_signed w = []"
assume jj: "bv_msb w \<noteq> \<zero>"
have "\<zero> = bv_msb (norm_signed w)" by (subst ii) simp
also have "... \<noteq> \<zero>" by (simp add: jj)
finally show False by simp
qed
also have "... \<le> length w"
by (rule norm_signed_length)
finally show ?thesis .
qed
lemma length_int_to_bv_lower_limit_gt0:
assumes wk: "2 ^ (k - 1) \<le> i"
shows "k < length (int_to_bv i)"
proof (rule ccontr)
have "0 < (2::int) ^ (k - 1)"
by (rule zero_less_power) simp
also have "... \<le> i" by (rule wk)
finally have i0: "0 < i" .
have lii0: "0 < length (int_to_bv i)"
apply (rule pos_length_pos)
apply (simp,rule i0)
done
assume "~ k < length (int_to_bv i)"
hence "length (int_to_bv i) \<le> k" by simp
with lii0
have a: "length (int_to_bv i) - 1 \<le> k - 1"
by arith
have "i < 2 ^ (length (int_to_bv i) - 1)"
proof -
have "i = bv_to_int (int_to_bv i)"
by simp
also have "... < 2 ^ (length (int_to_bv i) - 1)"
by (rule bv_to_int_upper_range)
finally show ?thesis .
qed
also have "(2::int) ^ (length (int_to_bv i) - 1) \<le> 2 ^ (k - 1)" using a
by simp
finally have "i < 2 ^ (k - 1)" .
with wk show False by simp
qed
lemma length_int_to_bv_upper_limit_lem1:
assumes w1: "i < -1"
and wk: "- (2 ^ (k - 1)) \<le> i"
shows "length (int_to_bv i) \<le> k"
proof (rule ccontr)
from w1 wk
have k1: "1 < k" by (cases "k - 1") simp_all
assume "~ length (int_to_bv i) \<le> k"
hence "k < length (int_to_bv i)" by simp
hence "k \<le> length (int_to_bv i) - 1" by arith
hence a: "k - 1 \<le> length (int_to_bv i) - 2" by arith
have "i < - (2 ^ (length (int_to_bv i) - 2))"
proof -
have "i = bv_to_int (int_to_bv i)"
by simp
also have "... < - (2 ^ (length (norm_signed (int_to_bv i)) - 2))"
by (rule bv_to_int_upper_limit_lem1,simp,rule w1)
finally show ?thesis by simp
qed
also have "... \<le> -(2 ^ (k - 1))"
proof -
have "(2::int) ^ (k - 1) \<le> 2 ^ (length (int_to_bv i) - 2)" using a by simp
thus ?thesis by simp
qed
finally have "i < -(2 ^ (k - 1))" .
with wk show False by simp
qed
lemma length_int_to_bv_lower_limit_lem1:
assumes wk: "i < -(2 ^ (k - 1))"
shows "k < length (int_to_bv i)"
proof (rule ccontr)
from wk have "i \<le> -(2 ^ (k - 1)) - 1" by simp
also have "... < -1"
proof -
have "0 < (2::int) ^ (k - 1)"
by (rule zero_less_power) simp
hence "-((2::int) ^ (k - 1)) < 0" by simp
thus ?thesis by simp
qed
finally have i1: "i < -1" .
have lii0: "0 < length (int_to_bv i)"
apply (rule neg_length_pos)
apply (simp, rule i1)
done
assume "~ k < length (int_to_bv i)"
hence "length (int_to_bv i) \<le> k"
by simp
with lii0 have a: "length (int_to_bv i) - 1 \<le> k - 1" by arith
hence "(2::int) ^ (length (int_to_bv i) - 1) \<le> 2 ^ (k - 1)" by simp
hence "-((2::int) ^ (k - 1)) \<le> - (2 ^ (length (int_to_bv i) - 1))" by simp
also have "... \<le> i"
proof -
have "- (2 ^ (length (int_to_bv i) - 1)) \<le> bv_to_int (int_to_bv i)"
by (rule bv_to_int_lower_range)
also have "... = i"
by simp
finally show ?thesis .
qed
finally have "-(2 ^ (k - 1)) \<le> i" .
with wk show False by simp
qed
subsection {* Signed Arithmetic Operations *}
subsubsection {* Conversion from unsigned to signed *}
definition
utos :: "bit list => bit list" where
"utos w = norm_signed (\<zero> # w)"
lemma utos_type [simp]: "utos (norm_unsigned w) = utos w"
by (simp add: utos_def norm_signed_Cons)
lemma utos_returntype [simp]: "norm_signed (utos w) = utos w"
by (simp add: utos_def)
lemma utos_length: "length (utos w) \<le> Suc (length w)"
by (simp add: utos_def norm_signed_Cons)
lemma bv_to_int_utos: "bv_to_int (utos w) = int (bv_to_nat w)"
proof (simp add: utos_def norm_signed_Cons, safe)
assume "norm_unsigned w = []"
hence "bv_to_nat (norm_unsigned w) = 0" by simp
thus "bv_to_nat w = 0" by simp
qed
subsubsection {* Unary minus *}
definition
bv_uminus :: "bit list => bit list" where
"bv_uminus w = int_to_bv (- bv_to_int w)"
lemma bv_uminus_type [simp]: "bv_uminus (norm_signed w) = bv_uminus w"
by (simp add: bv_uminus_def)
lemma bv_uminus_returntype [simp]: "norm_signed (bv_uminus w) = bv_uminus w"
by (simp add: bv_uminus_def)
lemma bv_uminus_length: "length (bv_uminus w) \<le> Suc (length w)"
proof -
have "1 < -bv_to_int w \<or> -bv_to_int w = 1 \<or> -bv_to_int w = 0 \<or> -bv_to_int w = -1 \<or> -bv_to_int w < -1"
by arith
thus ?thesis
proof safe
assume p: "1 < - bv_to_int w"
have lw: "0 < length w"
apply (rule neg_length_pos)
using p
apply simp
done
show ?thesis
proof (simp add: bv_uminus_def,rule length_int_to_bv_upper_limit_gt0,simp_all)
from prems show "bv_to_int w < 0" by simp
next
have "-(2^(length w - 1)) \<le> bv_to_int w"
by (rule bv_to_int_lower_range)
hence "- bv_to_int w \<le> 2^(length w - 1)" by simp
also from lw have "... < 2 ^ length w" by simp
finally show "- bv_to_int w < 2 ^ length w" by simp
qed
next
assume p: "- bv_to_int w = 1"
hence lw: "0 < length w" by (cases w) simp_all
from p
show ?thesis
apply (simp add: bv_uminus_def)
using lw
apply (simp (no_asm) add: nat_to_bv_non0)
done
next
assume "- bv_to_int w = 0"
thus ?thesis by (simp add: bv_uminus_def)
next
assume p: "- bv_to_int w = -1"
thus ?thesis by (simp add: bv_uminus_def)
next
assume p: "- bv_to_int w < -1"
show ?thesis
apply (simp add: bv_uminus_def)
apply (rule length_int_to_bv_upper_limit_lem1)
apply (rule p)
apply simp
proof -
have "bv_to_int w < 2 ^ (length w - 1)"
by (rule bv_to_int_upper_range)
also have "... \<le> 2 ^ length w" by simp
finally show "bv_to_int w \<le> 2 ^ length w" by simp
qed
qed
qed
lemma bv_uminus_length_utos: "length (bv_uminus (utos w)) \<le> Suc (length w)"
proof -
have "-bv_to_int (utos w) = 0 \<or> -bv_to_int (utos w) = -1 \<or> -bv_to_int (utos w) < -1"
by (simp add: bv_to_int_utos, arith)
thus ?thesis
proof safe
assume "-bv_to_int (utos w) = 0"
thus ?thesis by (simp add: bv_uminus_def)
next
assume "-bv_to_int (utos w) = -1"
thus ?thesis by (simp add: bv_uminus_def)
next
assume p: "-bv_to_int (utos w) < -1"
show ?thesis
apply (simp add: bv_uminus_def)
apply (rule length_int_to_bv_upper_limit_lem1)
apply (rule p)
apply (simp add: bv_to_int_utos)
using bv_to_nat_upper_range [of w]
apply (simp add: int_nat_two_exp)
done
qed
qed
definition
bv_sadd :: "[bit list, bit list ] => bit list" where
"bv_sadd w1 w2 = int_to_bv (bv_to_int w1 + bv_to_int w2)"
lemma bv_sadd_type1 [simp]: "bv_sadd (norm_signed w1) w2 = bv_sadd w1 w2"
by (simp add: bv_sadd_def)
lemma bv_sadd_type2 [simp]: "bv_sadd w1 (norm_signed w2) = bv_sadd w1 w2"
by (simp add: bv_sadd_def)
lemma bv_sadd_returntype [simp]: "norm_signed (bv_sadd w1 w2) = bv_sadd w1 w2"
by (simp add: bv_sadd_def)
lemma adder_helper:
assumes lw: "0 < max (length w1) (length w2)"
shows "((2::int) ^ (length w1 - 1)) + (2 ^ (length w2 - 1)) \<le> 2 ^ max (length w1) (length w2)"
proof -
have "((2::int) ^ (length w1 - 1)) + (2 ^ (length w2 - 1)) \<le>
2 ^ (max (length w1) (length w2) - 1) + 2 ^ (max (length w1) (length w2) - 1)"
apply (cases "length w1 \<le> length w2")
apply (auto simp add: max_def)
done
also have "... = 2 ^ max (length w1) (length w2)"
proof -
from lw
show ?thesis
apply simp
apply (subst power_Suc [symmetric])
apply (simp del: power.simps)
done
qed
finally show ?thesis .
qed
lemma bv_sadd_length: "length (bv_sadd w1 w2) \<le> Suc (max (length w1) (length w2))"
proof -
let ?Q = "bv_to_int w1 + bv_to_int w2"
have helper: "?Q \<noteq> 0 ==> 0 < max (length w1) (length w2)"
proof -
assume p: "?Q \<noteq> 0"
show "0 < max (length w1) (length w2)"
proof (simp add: less_max_iff_disj,rule)
assume [simp]: "w1 = []"
show "w2 \<noteq> []"
proof (rule ccontr,simp)
assume [simp]: "w2 = []"
from p show False by simp
qed
qed
qed
have "0 < ?Q \<or> ?Q = 0 \<or> ?Q = -1 \<or> ?Q < -1" by arith
thus ?thesis
proof safe
assume "?Q = 0"
thus ?thesis
by (simp add: bv_sadd_def)
next
assume "?Q = -1"
thus ?thesis
by (simp add: bv_sadd_def)
next
assume p: "0 < ?Q"
show ?thesis
apply (simp add: bv_sadd_def)
apply (rule length_int_to_bv_upper_limit_gt0)
apply (rule p)
proof simp
from bv_to_int_upper_range [of w2]
have "bv_to_int w2 \<le> 2 ^ (length w2 - 1)"
by simp
with bv_to_int_upper_range [of w1]
have "bv_to_int w1 + bv_to_int w2 < (2 ^ (length w1 - 1)) + (2 ^ (length w2 - 1))"
by (rule zadd_zless_mono)
also have "... \<le> 2 ^ max (length w1) (length w2)"
apply (rule adder_helper)
apply (rule helper)
using p
apply simp
done
finally show "?Q < 2 ^ max (length w1) (length w2)" .
qed
next
assume p: "?Q < -1"
show ?thesis
apply (simp add: bv_sadd_def)
apply (rule length_int_to_bv_upper_limit_lem1,simp_all)
apply (rule p)
proof -
have "(2 ^ (length w1 - 1)) + 2 ^ (length w2 - 1) \<le> (2::int) ^ max (length w1) (length w2)"
apply (rule adder_helper)
apply (rule helper)
using p
apply simp
done
hence "-((2::int) ^ max (length w1) (length w2)) \<le> - (2 ^ (length w1 - 1)) + -(2 ^ (length w2 - 1))"
by simp
also have "- (2 ^ (length w1 - 1)) + -(2 ^ (length w2 - 1)) \<le> ?Q"
apply (rule add_mono)
apply (rule bv_to_int_lower_range [of w1])
apply (rule bv_to_int_lower_range [of w2])
done
finally show "- (2^max (length w1) (length w2)) \<le> ?Q" .
qed
qed
qed
definition
bv_sub :: "[bit list, bit list] => bit list" where
"bv_sub w1 w2 = bv_sadd w1 (bv_uminus w2)"
lemma bv_sub_type1 [simp]: "bv_sub (norm_signed w1) w2 = bv_sub w1 w2"
by (simp add: bv_sub_def)
lemma bv_sub_type2 [simp]: "bv_sub w1 (norm_signed w2) = bv_sub w1 w2"
by (simp add: bv_sub_def)
lemma bv_sub_returntype [simp]: "norm_signed (bv_sub w1 w2) = bv_sub w1 w2"
by (simp add: bv_sub_def)
lemma bv_sub_length: "length (bv_sub w1 w2) \<le> Suc (max (length w1) (length w2))"
proof (cases "bv_to_int w2 = 0")
assume p: "bv_to_int w2 = 0"
show ?thesis
proof (simp add: bv_sub_def bv_sadd_def bv_uminus_def p)
have "length (norm_signed w1) \<le> length w1"
by (rule norm_signed_length)
also have "... \<le> max (length w1) (length w2)"
by (rule le_maxI1)
also have "... \<le> Suc (max (length w1) (length w2))"
by arith
finally show "length (norm_signed w1) \<le> Suc (max (length w1) (length w2))" .
qed
next
assume "bv_to_int w2 \<noteq> 0"
hence "0 < length w2" by (cases w2,simp_all)
hence lmw: "0 < max (length w1) (length w2)" by arith
let ?Q = "bv_to_int w1 - bv_to_int w2"
have "0 < ?Q \<or> ?Q = 0 \<or> ?Q = -1 \<or> ?Q < -1" by arith
thus ?thesis
proof safe
assume "?Q = 0"
thus ?thesis
by (simp add: bv_sub_def bv_sadd_def bv_uminus_def)
next
assume "?Q = -1"
thus ?thesis
by (simp add: bv_sub_def bv_sadd_def bv_uminus_def)
next
assume p: "0 < ?Q"
show ?thesis
apply (simp add: bv_sub_def bv_sadd_def bv_uminus_def)
apply (rule length_int_to_bv_upper_limit_gt0)
apply (rule p)
proof simp
from bv_to_int_lower_range [of w2]
have v2: "- bv_to_int w2 \<le> 2 ^ (length w2 - 1)" by simp
have "bv_to_int w1 + - bv_to_int w2 < (2 ^ (length w1 - 1)) + (2 ^ (length w2 - 1))"
apply (rule zadd_zless_mono)
apply (rule bv_to_int_upper_range [of w1])
apply (rule v2)
done
also have "... \<le> 2 ^ max (length w1) (length w2)"
apply (rule adder_helper)
apply (rule lmw)
done
finally show "?Q < 2 ^ max (length w1) (length w2)" by simp
qed
next
assume p: "?Q < -1"
show ?thesis
apply (simp add: bv_sub_def bv_sadd_def bv_uminus_def)
apply (rule length_int_to_bv_upper_limit_lem1)
apply (rule p)
proof simp
have "(2 ^ (length w1 - 1)) + 2 ^ (length w2 - 1) \<le> (2::int) ^ max (length w1) (length w2)"
apply (rule adder_helper)
apply (rule lmw)
done
hence "-((2::int) ^ max (length w1) (length w2)) \<le> - (2 ^ (length w1 - 1)) + -(2 ^ (length w2 - 1))"
by simp
also have "- (2 ^ (length w1 - 1)) + -(2 ^ (length w2 - 1)) \<le> bv_to_int w1 + -bv_to_int w2"
apply (rule add_mono)
apply (rule bv_to_int_lower_range [of w1])
using bv_to_int_upper_range [of w2]
apply simp
done
finally show "- (2^max (length w1) (length w2)) \<le> ?Q" by simp
qed
qed
qed
definition
bv_smult :: "[bit list, bit list] => bit list" where
"bv_smult w1 w2 = int_to_bv (bv_to_int w1 * bv_to_int w2)"
lemma bv_smult_type1 [simp]: "bv_smult (norm_signed w1) w2 = bv_smult w1 w2"
by (simp add: bv_smult_def)
lemma bv_smult_type2 [simp]: "bv_smult w1 (norm_signed w2) = bv_smult w1 w2"
by (simp add: bv_smult_def)
lemma bv_smult_returntype [simp]: "norm_signed (bv_smult w1 w2) = bv_smult w1 w2"
by (simp add: bv_smult_def)
lemma bv_smult_length: "length (bv_smult w1 w2) \<le> length w1 + length w2"
proof -
let ?Q = "bv_to_int w1 * bv_to_int w2"
have lmw: "?Q \<noteq> 0 ==> 0 < length w1 \<and> 0 < length w2" by auto
have "0 < ?Q \<or> ?Q = 0 \<or> ?Q = -1 \<or> ?Q < -1" by arith
thus ?thesis
proof (safe dest!: iffD1 [OF mult_eq_0_iff])
assume "bv_to_int w1 = 0"
thus ?thesis by (simp add: bv_smult_def)
next
assume "bv_to_int w2 = 0"
thus ?thesis by (simp add: bv_smult_def)
next
assume p: "?Q = -1"
show ?thesis
apply (simp add: bv_smult_def p)
apply (cut_tac lmw)
apply arith
using p
apply simp
done
next
assume p: "0 < ?Q"
thus ?thesis
proof (simp add: zero_less_mult_iff,safe)
assume bi1: "0 < bv_to_int w1"
assume bi2: "0 < bv_to_int w2"
show ?thesis
apply (simp add: bv_smult_def)
apply (rule length_int_to_bv_upper_limit_gt0)
apply (rule p)
proof simp
have "?Q < 2 ^ (length w1 - 1) * 2 ^ (length w2 - 1)"
apply (rule mult_strict_mono)
apply (rule bv_to_int_upper_range)
apply (rule bv_to_int_upper_range)
apply (rule zero_less_power)
apply simp
using bi2
apply simp
done
also have "... \<le> 2 ^ (length w1 + length w2 - Suc 0)"
apply simp
apply (subst zpower_zadd_distrib [symmetric])
apply simp
done
finally show "?Q < 2 ^ (length w1 + length w2 - Suc 0)" .
qed
next
assume bi1: "bv_to_int w1 < 0"
assume bi2: "bv_to_int w2 < 0"
show ?thesis
apply (simp add: bv_smult_def)
apply (rule length_int_to_bv_upper_limit_gt0)
apply (rule p)
proof simp
have "-bv_to_int w1 * -bv_to_int w2 \<le> 2 ^ (length w1 - 1) * 2 ^(length w2 - 1)"
apply (rule mult_mono)
using bv_to_int_lower_range [of w1]
apply simp
using bv_to_int_lower_range [of w2]
apply simp
apply (rule zero_le_power,simp)
using bi2
apply simp
done
hence "?Q \<le> 2 ^ (length w1 - 1) * 2 ^(length w2 - 1)"
by simp
also have "... < 2 ^ (length w1 + length w2 - Suc 0)"
apply simp
apply (subst zpower_zadd_distrib [symmetric])
apply simp
apply (cut_tac lmw)
apply arith
apply (cut_tac p)
apply arith
done
finally show "?Q < 2 ^ (length w1 + length w2 - Suc 0)" .
qed
qed
next
assume p: "?Q < -1"
show ?thesis
apply (subst bv_smult_def)
apply (rule length_int_to_bv_upper_limit_lem1)
apply (rule p)
proof simp
have "(2::int) ^ (length w1 - 1) * 2 ^(length w2 - 1) \<le> 2 ^ (length w1 + length w2 - Suc 0)"
apply simp
apply (subst zpower_zadd_distrib [symmetric])
apply simp
done
hence "-((2::int) ^ (length w1 + length w2 - Suc 0)) \<le> -(2^(length w1 - 1) * 2 ^ (length w2 - 1))"
by simp
also have "... \<le> ?Q"
proof -
from p
have q: "bv_to_int w1 * bv_to_int w2 < 0"
by simp
thus ?thesis
proof (simp add: mult_less_0_iff,safe)
assume bi1: "0 < bv_to_int w1"
assume bi2: "bv_to_int w2 < 0"
have "-bv_to_int w2 * bv_to_int w1 \<le> ((2::int)^(length w2 - 1)) * (2 ^ (length w1 - 1))"
apply (rule mult_mono)
using bv_to_int_lower_range [of w2]
apply simp
using bv_to_int_upper_range [of w1]
apply simp
apply (rule zero_le_power,simp)
using bi1
apply simp
done
hence "-?Q \<le> ((2::int)^(length w1 - 1)) * (2 ^ (length w2 - 1))"
by (simp add: zmult_ac)
thus "-(((2::int)^(length w1 - Suc 0)) * (2 ^ (length w2 - Suc 0))) \<le> ?Q"
by simp
next
assume bi1: "bv_to_int w1 < 0"
assume bi2: "0 < bv_to_int w2"
have "-bv_to_int w1 * bv_to_int w2 \<le> ((2::int)^(length w1 - 1)) * (2 ^ (length w2 - 1))"
apply (rule mult_mono)
using bv_to_int_lower_range [of w1]
apply simp
using bv_to_int_upper_range [of w2]
apply simp
apply (rule zero_le_power,simp)
using bi2
apply simp
done
hence "-?Q \<le> ((2::int)^(length w1 - 1)) * (2 ^ (length w2 - 1))"
by (simp add: zmult_ac)
thus "-(((2::int)^(length w1 - Suc 0)) * (2 ^ (length w2 - Suc 0))) \<le> ?Q"
by simp
qed
qed
finally show "-(2 ^ (length w1 + length w2 - Suc 0)) \<le> ?Q" .
qed
qed
qed
lemma bv_msb_one: "bv_msb w = \<one> ==> bv_to_nat w \<noteq> 0"
by (cases w) simp_all
lemma bv_smult_length_utos: "length (bv_smult (utos w1) w2) \<le> length w1 + length w2"
proof -
let ?Q = "bv_to_int (utos w1) * bv_to_int w2"
have lmw: "?Q \<noteq> 0 ==> 0 < length (utos w1) \<and> 0 < length w2" by auto
have "0 < ?Q \<or> ?Q = 0 \<or> ?Q = -1 \<or> ?Q < -1" by arith
thus ?thesis
proof (safe dest!: iffD1 [OF mult_eq_0_iff])
assume "bv_to_int (utos w1) = 0"
thus ?thesis by (simp add: bv_smult_def)
next
assume "bv_to_int w2 = 0"
thus ?thesis by (simp add: bv_smult_def)
next
assume p: "0 < ?Q"
thus ?thesis
proof (simp add: zero_less_mult_iff,safe)
assume biw2: "0 < bv_to_int w2"
show ?thesis
apply (simp add: bv_smult_def)
apply (rule length_int_to_bv_upper_limit_gt0)
apply (rule p)
proof simp
have "?Q < 2 ^ length w1 * 2 ^ (length w2 - 1)"
apply (rule mult_strict_mono)
apply (simp add: bv_to_int_utos int_nat_two_exp)
apply (rule bv_to_nat_upper_range)
apply (rule bv_to_int_upper_range)
apply (rule zero_less_power,simp)
using biw2
apply simp
done
also have "... \<le> 2 ^ (length w1 + length w2 - Suc 0)"
apply simp
apply (subst zpower_zadd_distrib [symmetric])
apply simp
apply (cut_tac lmw)
apply arith
using p
apply auto
done
finally show "?Q < 2 ^ (length w1 + length w2 - Suc 0)" .
qed
next
assume "bv_to_int (utos w1) < 0"
thus ?thesis by (simp add: bv_to_int_utos)
qed
next
assume p: "?Q = -1"
thus ?thesis
apply (simp add: bv_smult_def)
apply (cut_tac lmw)
apply arith
apply simp
done
next
assume p: "?Q < -1"
show ?thesis
apply (subst bv_smult_def)
apply (rule length_int_to_bv_upper_limit_lem1)
apply (rule p)
proof simp
have "(2::int) ^ length w1 * 2 ^(length w2 - 1) \<le> 2 ^ (length w1 + length w2 - Suc 0)"
apply simp
apply (subst zpower_zadd_distrib [symmetric])
apply simp
apply (cut_tac lmw)
apply arith
apply (cut_tac p)
apply arith
done
hence "-((2::int) ^ (length w1 + length w2 - Suc 0)) \<le> -(2^ length w1 * 2 ^ (length w2 - 1))"
by simp
also have "... \<le> ?Q"
proof -
from p
have q: "bv_to_int (utos w1) * bv_to_int w2 < 0"
by simp
thus ?thesis
proof (simp add: mult_less_0_iff,safe)
assume bi1: "0 < bv_to_int (utos w1)"
assume bi2: "bv_to_int w2 < 0"
have "-bv_to_int w2 * bv_to_int (utos w1) \<le> ((2::int)^(length w2 - 1)) * (2 ^ length w1)"
apply (rule mult_mono)
using bv_to_int_lower_range [of w2]
apply simp
apply (simp add: bv_to_int_utos)
using bv_to_nat_upper_range [of w1]
apply (simp add: int_nat_two_exp)
apply (rule zero_le_power,simp)
using bi1
apply simp
done
hence "-?Q \<le> ((2::int)^length w1) * (2 ^ (length w2 - 1))"
by (simp add: zmult_ac)
thus "-(((2::int)^length w1) * (2 ^ (length w2 - Suc 0))) \<le> ?Q"
by simp
next
assume bi1: "bv_to_int (utos w1) < 0"
thus "-(((2::int)^length w1) * (2 ^ (length w2 - Suc 0))) \<le> ?Q"
by (simp add: bv_to_int_utos)
qed
qed
finally show "-(2 ^ (length w1 + length w2 - Suc 0)) \<le> ?Q" .
qed
qed
qed
lemma bv_smult_sym: "bv_smult w1 w2 = bv_smult w2 w1"
by (simp add: bv_smult_def zmult_ac)
subsection {* Structural operations *}
definition
bv_select :: "[bit list,nat] => bit" where
"bv_select w i = w ! (length w - 1 - i)"
definition
bv_chop :: "[bit list,nat] => bit list * bit list" where
"bv_chop w i = (let len = length w in (take (len - i) w,drop (len - i) w))"
definition
bv_slice :: "[bit list,nat*nat] => bit list" where
"bv_slice w = (\<lambda>(b,e). fst (bv_chop (snd (bv_chop w (b+1))) e))"
lemma bv_select_rev:
assumes notnull: "n < length w"
shows "bv_select w n = rev w ! n"
proof -
have "\<forall>n. n < length w --> bv_select w n = rev w ! n"
proof (rule length_induct [of _ w],auto simp add: bv_select_def)
fix xs :: "bit list"
fix n
assume ind: "\<forall>ys::bit list. length ys < length xs --> (\<forall>n. n < length ys --> ys ! (length ys - Suc n) = rev ys ! n)"
assume notx: "n < length xs"
show "xs ! (length xs - Suc n) = rev xs ! n"
proof (cases xs)
assume "xs = []"
with notx show ?thesis by simp
next
fix y ys
assume [simp]: "xs = y # ys"
show ?thesis
proof (auto simp add: nth_append)
assume noty: "n < length ys"
from spec [OF ind,of ys]
have "\<forall>n. n < length ys --> ys ! (length ys - Suc n) = rev ys ! n"
by simp
hence "n < length ys --> ys ! (length ys - Suc n) = rev ys ! n" ..
from this and noty
have "ys ! (length ys - Suc n) = rev ys ! n" ..
thus "(y # ys) ! (length ys - n) = rev ys ! n"
by (simp add: nth_Cons' noty linorder_not_less [symmetric])
next
assume "~ n < length ys"
hence x: "length ys \<le> n" by simp
from notx have "n < Suc (length ys)" by simp
hence "n \<le> length ys" by simp
with x have "length ys = n" by simp
thus "y = [y] ! (n - length ys)" by simp
qed
qed
qed
then have "n < length w --> bv_select w n = rev w ! n" ..
from this and notnull show ?thesis ..
qed
lemma bv_chop_append: "bv_chop (w1 @ w2) (length w2) = (w1,w2)"
by (simp add: bv_chop_def Let_def)
lemma append_bv_chop_id: "fst (bv_chop w l) @ snd (bv_chop w l) = w"
by (simp add: bv_chop_def Let_def)
lemma bv_chop_length_fst [simp]: "length (fst (bv_chop w i)) = length w - i"
by (simp add: bv_chop_def Let_def)
lemma bv_chop_length_snd [simp]: "length (snd (bv_chop w i)) = min i (length w)"
by (simp add: bv_chop_def Let_def)
lemma bv_slice_length [simp]: "[| j \<le> i; i < length w |] ==> length (bv_slice w (i,j)) = i - j + 1"
by (auto simp add: bv_slice_def)
definition
length_nat :: "nat => nat" where
"length_nat x = (LEAST n. x < 2 ^ n)"
lemma length_nat: "length (nat_to_bv n) = length_nat n"
apply (simp add: length_nat_def)
apply (rule Least_equality [symmetric])
prefer 2
apply (rule length_nat_to_bv_upper_limit)
apply arith
apply (rule ccontr)
proof -
assume "~ n < 2 ^ length (nat_to_bv n)"
hence "2 ^ length (nat_to_bv n) \<le> n" by simp
hence "length (nat_to_bv n) < length (nat_to_bv n)"
by (rule length_nat_to_bv_lower_limit)
thus False by simp
qed
lemma length_nat_0 [simp]: "length_nat 0 = 0"
by (simp add: length_nat_def Least_equality)
lemma length_nat_non0:
assumes n0: "n \<noteq> 0"
shows "length_nat n = Suc (length_nat (n div 2))"
apply (simp add: length_nat [symmetric])
apply (subst nat_to_bv_non0 [of n])
apply (simp_all add: n0)
done
definition
length_int :: "int => nat" where
"length_int x =
(if 0 < x then Suc (length_nat (nat x))
else if x = 0 then 0
else Suc (length_nat (nat (-x - 1))))"
lemma length_int: "length (int_to_bv i) = length_int i"
proof (cases "0 < i")
assume i0: "0 < i"
hence "length (int_to_bv i) =
length (norm_signed (\<zero> # norm_unsigned (nat_to_bv (nat i))))" by simp
also from norm_unsigned_result [of "nat_to_bv (nat i)"]
have "... = Suc (length_nat (nat i))"
apply safe
apply (simp del: norm_unsigned_nat_to_bv)
apply (drule norm_empty_bv_to_nat_zero)
using prems
apply simp
apply (cases "norm_unsigned (nat_to_bv (nat i))")
apply (drule norm_empty_bv_to_nat_zero [of "nat_to_bv (nat i)"])
using prems
apply simp
apply simp
using prems
apply (simp add: length_nat [symmetric])
done
finally show ?thesis
using i0
by (simp add: length_int_def)
next
assume "~ 0 < i"
hence i0: "i \<le> 0" by simp
show ?thesis
proof (cases "i = 0")
assume "i = 0"
thus ?thesis by (simp add: length_int_def)
next
assume "i \<noteq> 0"
with i0 have i0: "i < 0" by simp
hence "length (int_to_bv i) =
length (norm_signed (\<one> # bv_not (norm_unsigned (nat_to_bv (nat (- i) - 1)))))"
by (simp add: int_to_bv_def nat_diff_distrib)
also from norm_unsigned_result [of "nat_to_bv (nat (- i) - 1)"]
have "... = Suc (length_nat (nat (- i) - 1))"
apply safe
apply (simp del: norm_unsigned_nat_to_bv)
apply (drule norm_empty_bv_to_nat_zero [of "nat_to_bv (nat (-i) - Suc 0)"])
using prems
apply simp
apply (cases "- i - 1 = 0")
apply simp
apply (simp add: length_nat [symmetric])
apply (cases "norm_unsigned (nat_to_bv (nat (- i) - 1))")
apply simp
apply simp
done
finally
show ?thesis
using i0 by (simp add: length_int_def nat_diff_distrib del: int_to_bv_lt0)
qed
qed
lemma length_int_0 [simp]: "length_int 0 = 0"
by (simp add: length_int_def)
lemma length_int_gt0: "0 < i ==> length_int i = Suc (length_nat (nat i))"
by (simp add: length_int_def)
lemma length_int_lt0: "i < 0 ==> length_int i = Suc (length_nat (nat (- i) - 1))"
by (simp add: length_int_def nat_diff_distrib)
lemma bv_chopI: "[| w = w1 @ w2 ; i = length w2 |] ==> bv_chop w i = (w1,w2)"
by (simp add: bv_chop_def Let_def)
lemma bv_sliceI: "[| j \<le> i ; i < length w ; w = w1 @ w2 @ w3 ; Suc i = length w2 + j ; j = length w3 |] ==> bv_slice w (i,j) = w2"
apply (simp add: bv_slice_def)
apply (subst bv_chopI [of "w1 @ w2 @ w3" w1 "w2 @ w3"])
apply simp
apply simp
apply simp
apply (subst bv_chopI [of "w2 @ w3" w2 w3],simp_all)
done
lemma bv_slice_bv_slice:
assumes ki: "k \<le> i"
and ij: "i \<le> j"
and jl: "j \<le> l"
and lw: "l < length w"
shows "bv_slice w (j,i) = bv_slice (bv_slice w (l,k)) (j-k,i-k)"
proof -
def w1 == "fst (bv_chop w (Suc l))"
and w2 == "fst (bv_chop (snd (bv_chop w (Suc l))) (Suc j))"
and w3 == "fst (bv_chop (snd (bv_chop (snd (bv_chop w (Suc l))) (Suc j))) i)"
and w4 == "fst (bv_chop (snd (bv_chop (snd (bv_chop (snd (bv_chop w (Suc l))) (Suc j))) i)) k)"
and w5 == "snd (bv_chop (snd (bv_chop (snd (bv_chop (snd (bv_chop w (Suc l))) (Suc j))) i)) k)"
note w_defs = this
have w_def: "w = w1 @ w2 @ w3 @ w4 @ w5"
by (simp add: w_defs append_bv_chop_id)
from ki ij jl lw
show ?thesis
apply (subst bv_sliceI [where ?j = i and ?i = j and ?w = w and ?w1.0 = "w1 @ w2" and ?w2.0 = w3 and ?w3.0 = "w4 @ w5"])
apply simp_all
apply (rule w_def)
apply (simp add: w_defs min_def)
apply (simp add: w_defs min_def)
apply (subst bv_sliceI [where ?j = k and ?i = l and ?w = w and ?w1.0 = w1 and ?w2.0 = "w2 @ w3 @ w4" and ?w3.0 = w5])
apply simp_all
apply (rule w_def)
apply (simp add: w_defs min_def)
apply (simp add: w_defs min_def)
apply (subst bv_sliceI [where ?j = "i-k" and ?i = "j-k" and ?w = "w2 @ w3 @ w4" and ?w1.0 = w2 and ?w2.0 = w3 and ?w3.0 = w4])
apply simp_all
apply (simp_all add: w_defs min_def)
done
qed
lemma bv_to_nat_extend [simp]: "bv_to_nat (bv_extend n \<zero> w) = bv_to_nat w"
apply (simp add: bv_extend_def)
apply (subst bv_to_nat_dist_append)
apply simp
apply (induct "n - length w")
apply simp_all
done
lemma bv_msb_extend_same [simp]: "bv_msb w = b ==> bv_msb (bv_extend n b w) = b"
apply (simp add: bv_extend_def)
apply (induct "n - length w")
apply simp_all
done
lemma bv_to_int_extend [simp]:
assumes a: "bv_msb w = b"
shows "bv_to_int (bv_extend n b w) = bv_to_int w"
proof (cases "bv_msb w")
assume [simp]: "bv_msb w = \<zero>"
with a have [simp]: "b = \<zero>" by simp
show ?thesis by (simp add: bv_to_int_def)
next
assume [simp]: "bv_msb w = \<one>"
with a have [simp]: "b = \<one>" by simp
show ?thesis
apply (simp add: bv_to_int_def)
apply (simp add: bv_extend_def)
apply (induct "n - length w",simp_all)
done
qed
lemma length_nat_mono [simp]: "x \<le> y ==> length_nat x \<le> length_nat y"
proof (rule ccontr)
assume xy: "x \<le> y"
assume "~ length_nat x \<le> length_nat y"
hence lxly: "length_nat y < length_nat x"
by simp
hence "length_nat y < (LEAST n. x < 2 ^ n)"
by (simp add: length_nat_def)
hence "~ x < 2 ^ length_nat y"
by (rule not_less_Least)
hence xx: "2 ^ length_nat y \<le> x"
by simp
have yy: "y < 2 ^ length_nat y"
apply (simp add: length_nat_def)
apply (rule LeastI)
apply (subgoal_tac "y < 2 ^ y",assumption)
apply (cases "0 \<le> y")
apply (induct y,simp_all)
done
with xx have "y < x" by simp
with xy show False by simp
qed
lemma length_nat_mono_int [simp]: "x \<le> y ==> length_nat x \<le> length_nat y"
by (rule length_nat_mono) arith
lemma length_nat_pos [simp,intro!]: "0 < x ==> 0 < length_nat x"
by (simp add: length_nat_non0)
lemma length_int_mono_gt0: "[| 0 \<le> x ; x \<le> y |] ==> length_int x \<le> length_int y"
by (cases "x = 0") (simp_all add: length_int_gt0 nat_le_eq_zle)
lemma length_int_mono_lt0: "[| x \<le> y ; y \<le> 0 |] ==> length_int y \<le> length_int x"
by (cases "y = 0") (simp_all add: length_int_lt0)
lemmas [simp] = length_nat_non0
lemma "nat_to_bv (number_of Numeral.Pls) = []"
by simp
consts
fast_bv_to_nat_helper :: "[bit list, int] => int"
primrec
fast_bv_to_nat_Nil: "fast_bv_to_nat_helper [] k = k"
fast_bv_to_nat_Cons: "fast_bv_to_nat_helper (b#bs) k =
fast_bv_to_nat_helper bs (k BIT (bit_case bit.B0 bit.B1 b))"
lemma fast_bv_to_nat_Cons0: "fast_bv_to_nat_helper (\<zero>#bs) bin =
fast_bv_to_nat_helper bs (bin BIT bit.B0)"
by simp
lemma fast_bv_to_nat_Cons1: "fast_bv_to_nat_helper (\<one>#bs) bin =
fast_bv_to_nat_helper bs (bin BIT bit.B1)"
by simp
lemma fast_bv_to_nat_def:
"bv_to_nat bs == number_of (fast_bv_to_nat_helper bs Numeral.Pls)"
proof (simp add: bv_to_nat_def)
have "\<forall> bin. \<not> (neg (number_of bin :: int)) \<longrightarrow> (foldl (%bn b. 2 * bn + bitval b) (number_of bin) bs) = number_of (fast_bv_to_nat_helper bs bin)"
apply (induct bs,simp)
apply (case_tac a,simp_all)
done
thus "foldl (\<lambda>bn b. 2 * bn + bitval b) 0 bs \<equiv> number_of (fast_bv_to_nat_helper bs Numeral.Pls)"
by (simp del: nat_numeral_0_eq_0 add: nat_numeral_0_eq_0 [symmetric])
qed
declare fast_bv_to_nat_Cons [simp del]
declare fast_bv_to_nat_Cons0 [simp]
declare fast_bv_to_nat_Cons1 [simp]
setup {*
(*comments containing lcp are the removal of fast_bv_of_nat*)
let
fun is_const_bool (Const("True",_)) = true
| is_const_bool (Const("False",_)) = true
| is_const_bool _ = false
fun is_const_bit (Const("Word.bit.Zero",_)) = true
| is_const_bit (Const("Word.bit.One",_)) = true
| is_const_bit _ = false
fun num_is_usable (Const("Numeral.Pls",_)) = true
| num_is_usable (Const("Numeral.Min",_)) = false
| num_is_usable (Const("Numeral.Bit",_) $ w $ b) =
num_is_usable w andalso is_const_bool b
| num_is_usable _ = false
fun vec_is_usable (Const("List.list.Nil",_)) = true
| vec_is_usable (Const("List.list.Cons",_) $ b $ bs) =
vec_is_usable bs andalso is_const_bit b
| vec_is_usable _ = false
(*lcp** val fast1_th = PureThy.get_thm thy "Word.fast_nat_to_bv_def"*)
val fast2_th = @{thm "Word.fast_bv_to_nat_def"};
(*lcp** fun f sg thms (Const("Word.nat_to_bv",_) $ (Const(@{const_name Numeral.number_of},_) $ t)) =
if num_is_usable t
then SOME (Drule.cterm_instantiate [(cterm_of sg (Var(("w",0),Type("IntDef.int",[]))),cterm_of sg t)] fast1_th)
else NONE
| f _ _ _ = NONE *)
fun g sg thms (Const("Word.bv_to_nat",_) $ (t as (Const("List.list.Cons",_) $ _ $ _))) =
if vec_is_usable t then
SOME (Drule.cterm_instantiate [(cterm_of sg (Var(("bs",0),Type("List.list",[Type("Word.bit",[])]))),cterm_of sg t)] fast2_th)
else NONE
| g _ _ _ = NONE
(*lcp** val simproc1 = Simplifier.simproc thy "nat_to_bv" ["Word.nat_to_bv (number_of w)"] f *)
val simproc2 = Simplifier.simproc @{theory} "bv_to_nat" ["Word.bv_to_nat (x # xs)"] g
in
(fn thy => (Simplifier.change_simpset_of thy (fn ss => ss addsimprocs [(*lcp*simproc1,*)simproc2]);
thy))
end*}
declare bv_to_nat1 [simp del]
declare bv_to_nat_helper [simp del]
definition
bv_mapzip :: "[bit => bit => bit,bit list, bit list] => bit list" where
"bv_mapzip f w1 w2 =
(let g = bv_extend (max (length w1) (length w2)) \<zero>
in map (split f) (zip (g w1) (g w2)))"
lemma bv_length_bv_mapzip [simp]:
"length (bv_mapzip f w1 w2) = max (length w1) (length w2)"
by (simp add: bv_mapzip_def Let_def split: split_max)
lemma bv_mapzip_Nil [simp]: "bv_mapzip f [] [] = []"
by (simp add: bv_mapzip_def Let_def)
lemma bv_mapzip_Cons [simp]: "length w1 = length w2 ==>
bv_mapzip f (x#w1) (y#w2) = f x y # bv_mapzip f w1 w2"
by (simp add: bv_mapzip_def Let_def)
end