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style(library/data/bv): Use syntax for dite

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Joe Hendrix 2015-12-01 09:20:32 -08:00 committed by Leonardo de Moura
parent 3574ad1f11
commit 719a78d541
1 changed files with 23 additions and 23 deletions
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46
library/data/bv.lean
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@ -38,36 +38,36 @@ section shift
-- shift left
definition bv_shl {n:ℕ} : bv n → ℕ → bv n
| x i :=
dite (i ≤ n)
(λle,
let r := dropn i x ++ replicate ff in
let eq := calc (n-i) + i = n : nat.sub_add_cancel le in
bv_cong eq r)
(λp, bv_zero n)
if le : i ≤ n then
let r := dropn i x ++ replicate ff in
let eq := calc (n-i) + i = n : nat.sub_add_cancel le in
bv_cong eq r
else
bv_zero n
-- unsigned shift right
definition bv_ushr {n:ℕ} : bv n → ℕ → bv n
| x i :=
dite (i ≤ n)
(λle,
let y : bv (n-i) := @firstn _ _ (n - i) (sub_le n i) x in
let eq := calc (i+(n-i)) = (n - i) + i : add.comm
... = n : nat.sub_add_cancel le in
bv_cong eq (replicate ff ++ y))
(λgt, bv_zero n)
if le : i ≤ n then
let y : bv (n-i) := @firstn _ _ (n - i) (sub_le n i) x in
let eq := calc (i+(n-i)) = (n - i) + i : add.comm
... = n : nat.sub_add_cancel le in
bv_cong eq (replicate ff ++ y)
else
bv_zero n
-- signed shift right
definition bv_sshr {m:ℕ} : bv (succ m) → ℕ → bv (succ m)
| x i :=
let n := succ m in
dite (i ≤ n)
(λle,
let z : bv i := replicate (head x) in
let y : bv (n-i) := @firstn _ _ (n - i) (sub_le n i) x in
let eq := calc (i+(n-i)) = (n-i) + i : add.comm
... = n : nat.sub_add_cancel le in
bv_cong eq (z ++ y))
(λgt, bv_zero n)
if le : i ≤ n then
let z : bv i := replicate (head x) in
let y : bv (n-i) := @firstn _ _ (n - i) (sub_le n i) x in
let eq := calc (i+(n-i)) = (n-i) + i : add.comm
... = n : nat.sub_add_cancel le in
bv_cong eq (z ++ y)
else
bv_zero n
end shift
@ -137,8 +137,8 @@ section arith
definition bv_slt : bv (succ n) → bv (succ n) → bool := λx y,
cond (head x)
(cond (head y)
(bv_ult (tail x) (tail y)) -- both negative
tt) -- x is negative and y is not
(bv_ult (tail x) (tail y)) -- both negative
tt) -- x is negative and y is not
(cond (head y)
ff -- y is negative and x is not
(bv_ult (tail x) (tail y))) -- both positive