changeset 314:891869ead775

...
author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Sat, 16 Sep 2023 11:40:13 +0900
parents 12fe78751331
children a067959c1799
files src/Putil.agda src/nat.agda src/sym5h.agda
diffstat 3 files changed, 570 insertions(+), 73 deletions(-) [+]
line wrap: on
line diff
--- a/src/Putil.agda	Fri Sep 15 23:36:43 2023 +0900
+++ b/src/Putil.agda	Sat Sep 16 11:40:13 2023 +0900
@@ -76,7 +76,7 @@
 pfill {n} {m} m≤n perm = pfill1 (n - m) (n-m<n n m ) (subst (λ k → Permutation k k ) (n-n-m=m m≤n ) perm) where
    pfill1 : (i : ℕ ) → i ≤ n  → Permutation (n - i) (n - i)  →  Permutation n n
    pfill1 0 _ perm = perm
-   pfill1 (suc i) i<n perm = pfill1 i (≤to< i<n) (subst (λ k → Permutation k k ) (si-sn=i-n i<n ) ( pprep perm ) )
+   pfill1 (suc i) i<n perm = pfill1 i (<to≤ i<n) (subst (λ k → Permutation k k ) (si-sn=i-n i<n ) ( pprep perm ) )
 
 --
 --  psawpim (inseert swap at position m )
@@ -376,6 +376,21 @@
           pleq2 : toℕ ( x ⟨$⟩ʳ (suc (fromℕ< i<sn)) ) ≡ toℕ ( y ⟨$⟩ʳ (suc (fromℕ< i<sn)) )
           pleq2 = headeq eq
 
+ℕL-inject : {h h1 : ℕ } {x y : List ℕ } → h ∷ x ≡ h1 ∷ y → h ≡ h1
+ℕL-inject refl = refl
+
+ℕL-inject-t : {h h1 : ℕ } {x y : List ℕ } → h ∷ x ≡ h1 ∷ y → x ≡ y
+ℕL-inject-t refl = refl
+                    
+ℕL-eq? : (x y : List ℕ ) → Dec (x ≡ y )  
+ℕL-eq? [] [] = yes refl                             
+ℕL-eq? [] (x ∷ y) = no (λ ())          
+ℕL-eq? (x ∷ x₁) [] = no (λ ())                 
+ℕL-eq? (h ∷ x) (h1 ∷ y) with h ≟ h1 | ℕL-eq? x y                               
+... | yes y1 | yes y2 = yes ( cong₂ (λ j k → j ∷ k ) y1 y2 )              
+... | yes y1 | no n = no (λ e → n (ℕL-inject-t e))                          
+... | no n  | t = no (λ e → n (ℕL-inject e))                              
+
 is-=p= : {n  : ℕ} → (x y : Permutation n n ) → Dec (x =p= y )
 is-=p= {zero} x y = yes record { peq = λ () }
 is-=p= {suc n} x y with ℕL-eq? (plist0 x ) ( plist0 y )
--- a/src/nat.agda	Fri Sep 15 23:36:43 2023 +0900
+++ b/src/nat.agda	Sat Sep 16 11:40:13 2023 +0900
@@ -7,9 +7,9 @@
 open import Relation.Nullary
 open import  Relation.Binary.PropositionalEquality
 open import  Relation.Binary.Core
-open import Relation.Binary.Definitions
+open import  Relation.Binary.Definitions
 open import  logic
-
+open import Level hiding ( zero ; suc ) 
 
 nat-<> : { x y : ℕ } → x < y → y < x → ⊥
 nat-<>  (s≤s x<y) (s≤s y<x) = nat-<> x<y y<x
@@ -30,14 +30,6 @@
 a<sa {zero} = s≤s z≤n
 a<sa {suc la} = s≤s a<sa 
 
-refl-≤s : {x : ℕ } → x ≤ suc x
-refl-≤s {zero} = z≤n
-refl-≤s {suc x} = s≤s (refl-≤s {x})
-
-a≤sa : {x : ℕ } → x ≤ suc x
-a≤sa {zero} = z≤n
-a≤sa {suc x} = s≤s (a≤sa {x})
-
 =→¬< : {x : ℕ  } → ¬ ( x < x )
 =→¬< {zero} ()
 =→¬< {suc x} (s≤s lt) = =→¬< lt
@@ -53,14 +45,13 @@
 <-∨ {suc x} {suc y} (s≤s lt) | case1 eq = case1 (cong (λ k → suc k ) eq)
 <-∨ {suc x} {suc y} (s≤s lt) | case2 lt1 = case2 (s≤s lt1)
 
-n≤n : (n : ℕ) →  n Data.Nat.≤ n
-n≤n zero = z≤n
-n≤n (suc n) = s≤s (n≤n n)
-
-<→m≤n : {m n : ℕ} → m  < n →  m Data.Nat.≤ n
-<→m≤n {zero} lt = z≤n
-<→m≤n {suc m} {zero} ()
-<→m≤n {suc m} {suc n} (s≤s lt) = s≤s (<→m≤n lt)
+≤-∨ : { x y : ℕ } → x ≤ y → ( (x ≡ y ) ∨ (x < y) )
+≤-∨ {zero} {zero} z≤n = case1 refl
+≤-∨ {zero} {suc y} z≤n = case2 (s≤s z≤n)
+≤-∨ {suc x} {zero} ()
+≤-∨ {suc x} {suc y} (s≤s lt) with ≤-∨ {x} {y} lt
+≤-∨ {suc x} {suc y} (s≤s lt) | case1 eq = case1 (cong (λ k → suc k ) eq)
+≤-∨ {suc x} {suc y} (s≤s lt) | case2 lt1 = case2 (s≤s lt1)
 
 max : (x y : ℕ) → ℕ
 max zero zero = zero
@@ -68,14 +59,78 @@
 max (suc x) zero = (suc x)
 max (suc x) (suc y) = suc ( max x y )
 
+x≤max : (x y : ℕ) → x ≤ max x y
+x≤max zero zero = ≤-refl
+x≤max zero (suc x) = z≤n
+x≤max (suc x) zero = ≤-refl
+x≤max (suc x) (suc y) = s≤s( x≤max x y )
+
+y≤max : (x y : ℕ) → y ≤ max x y
+y≤max zero zero = ≤-refl
+y≤max zero (suc x) = ≤-refl
+y≤max (suc x) zero = z≤n
+y≤max (suc x) (suc y) = s≤s( y≤max x y )
+
+x≤y→max=y : (x y : ℕ) → x ≤ y → max x y ≡ y
+x≤y→max=y zero zero x≤y = refl
+x≤y→max=y zero (suc y) x≤y = refl
+x≤y→max=y (suc x) (suc y) (s≤s x≤y) = cong suc (x≤y→max=y x y x≤y )
+
+y≤x→max=x : (x y : ℕ) → y ≤ x → max x y ≡ x
+y≤x→max=x zero zero y≤x = refl
+y≤x→max=x zero (suc y) ()
+y≤x→max=x (suc x) zero lt = refl
+y≤x→max=x (suc x) (suc y) (s≤s y≤x) = cong suc (y≤x→max=x x y y≤x )
+
 -- _*_ : ℕ → ℕ → ℕ
 -- _*_ zero _ = zero
 -- _*_ (suc n) m = m + ( n * m )
 
+-- x ^ y
 exp : ℕ → ℕ → ℕ
 exp _ zero = 1
 exp n (suc m) = n * ( exp n m )
 
+div2 : ℕ → (ℕ ∧ Bool )
+div2 zero =  ⟪ 0 , false ⟫
+div2 (suc zero) =  ⟪ 0 , true ⟫
+div2 (suc (suc n)) =  ⟪ suc (proj1 (div2 n)) , proj2 (div2 n) ⟫ where
+    open _∧_
+
+div2-rev : (ℕ ∧ Bool ) → ℕ
+div2-rev ⟪ x , true ⟫ = suc (x + x)
+div2-rev ⟪ x , false ⟫ = x + x
+
+div2-eq : (x : ℕ ) → div2-rev ( div2 x ) ≡ x
+div2-eq zero = refl
+div2-eq (suc zero) = refl
+div2-eq (suc (suc x)) with div2 x | inspect div2 x 
+... | ⟪ x1 , true ⟫ | record { eq = eq1 } = begin -- eq1 : div2 x ≡ ⟪ x1 , true ⟫
+     div2-rev ⟪ suc x1 , true ⟫ ≡⟨⟩
+     suc (suc (x1 + suc x1)) ≡⟨ cong (λ k → suc (suc k )) (+-comm x1  _ ) ⟩
+     suc (suc (suc (x1 + x1))) ≡⟨⟩    
+     suc (suc (div2-rev ⟪ x1 , true ⟫)) ≡⟨ cong (λ k → suc (suc (div2-rev k ))) (sym eq1) ⟩ 
+     suc (suc (div2-rev (div2 x)))      ≡⟨ cong (λ k → suc (suc k)) (div2-eq x) ⟩ 
+     suc (suc x) ∎  where open ≡-Reasoning
+... | ⟪ x1 , false ⟫ | record { eq = eq1 } = begin
+     div2-rev ⟪ suc x1 , false ⟫ ≡⟨⟩
+     suc (x1 + suc x1) ≡⟨ cong (λ k → (suc k )) (+-comm x1  _ ) ⟩
+     suc (suc (x1 + x1)) ≡⟨⟩    
+     suc (suc (div2-rev ⟪ x1 , false ⟫)) ≡⟨ cong (λ k → suc (suc (div2-rev k ))) (sym eq1) ⟩ 
+     suc (suc (div2-rev (div2 x)))      ≡⟨ cong (λ k → suc (suc k)) (div2-eq x) ⟩ 
+     suc (suc x) ∎  where open ≡-Reasoning
+
+sucprd : {i : ℕ } → 0 < i  → suc (pred i) ≡ i
+sucprd {suc i} 0<i = refl
+
+0<s : {x : ℕ } → zero < suc x
+0<s {_} = s≤s z≤n 
+
+px<py : {x y : ℕ } → pred x  < pred y → x < y
+px<py {zero} {suc y} lt = 0<s
+px<py {suc zero} {suc (suc y)} (s≤s lt) = s≤s 0<s
+px<py {suc (suc x)} {suc (suc y)} (s≤s lt) = s≤s (px<py {suc x} {suc y} lt)
+
 minus : (a b : ℕ ) →  ℕ
 minus a zero = a
 minus zero (suc b) = zero
@@ -83,6 +138,40 @@
 
 _-_ = minus
 
+sn-m=sn-m : {m n : ℕ } →  m ≤ n → suc n - m ≡ suc ( n - m )
+sn-m=sn-m {0} {n} z≤n = refl
+sn-m=sn-m {suc m} {suc n} (s≤s m<n) = sn-m=sn-m m<n
+
+si-sn=i-n : {i n : ℕ } → n < i  → suc (i - suc n) ≡ (i - n)
+si-sn=i-n {i} {n} n<i = begin
+   suc (i - suc n) ≡⟨ sym (sn-m=sn-m n<i )  ⟩
+   suc i - suc n ≡⟨⟩
+   i - n
+   ∎  where
+      open ≡-Reasoning
+
+refl-≤s : {x : ℕ } → x ≤ suc x
+refl-≤s {zero} = z≤n
+refl-≤s {suc x} = s≤s (refl-≤s {x})
+
+a≤sa = refl-≤s
+
+n-m<n : (n m : ℕ ) →  n - m ≤ n
+n-m<n zero zero = z≤n
+n-m<n (suc n) zero = s≤s (n-m<n n zero)
+n-m<n zero (suc m) = z≤n
+n-m<n (suc n) (suc m) = ≤-trans (n-m<n n m ) refl-≤s
+
+n-n-m=m : {m n : ℕ } → m ≤ n  → m ≡ (n - (n - m))
+n-n-m=m {0} {zero} z≤n = refl
+n-n-m=m {0} {suc n} z≤n = n-n-m=m {0} {n} z≤n
+n-n-m=m {suc m} {suc n} (s≤s m≤n) = sym ( begin
+   suc n - ( n - m )    ≡⟨ sn-m=sn-m (n-m<n  n m) ⟩
+   suc (n - ( n - m ))  ≡⟨ cong (λ k → suc k ) (sym (n-n-m=m m≤n)) ⟩
+   suc m
+   ∎  ) where
+      open ≡-Reasoning
+
 m+= : {i j  m : ℕ } → m + i ≡ m + j → i ≡ j
 m+= {i} {j} {zero} refl = refl
 m+= {i} {j} {suc m} eq = m+= {i} {j} {m} ( cong (λ k → pred k ) eq )
@@ -117,37 +206,6 @@
            suc x
         ∎  where open ≡-Reasoning
 
-sn-m=sn-m : {m n : ℕ } →  m ≤ n → suc n - m ≡ suc ( n - m )
-sn-m=sn-m {0} {n} z≤n = refl
-sn-m=sn-m {suc m} {suc n} (s≤s m<n) = sn-m=sn-m m<n
-
-si-sn=i-n : {i n : ℕ } → n < i  → suc (i - suc n) ≡ (i - n)
-si-sn=i-n {i} {n} n<i = begin
-   suc (i - suc n) ≡⟨ sym (sn-m=sn-m n<i )  ⟩
-   suc i - suc n ≡⟨⟩
-   i - n
-   ∎  where
-      open ≡-Reasoning
-
-n-m<n : (n m : ℕ ) →  n - m ≤ n
-n-m<n zero zero = z≤n
-n-m<n (suc n) zero = s≤s (n-m<n n zero)
-n-m<n zero (suc m) = z≤n
-n-m<n (suc n) (suc m) = ≤-trans (n-m<n n m ) refl-≤s
-
-n-n-m=m : {m n : ℕ } → m ≤ n  → m ≡ (n - (n - m))
-n-n-m=m {0} {zero} z≤n = refl
-n-n-m=m {0} {suc n} z≤n = n-n-m=m {0} {n} z≤n
-n-n-m=m {suc m} {suc n} (s≤s m≤n) = sym ( begin
-   suc n - ( n - m )    ≡⟨ sn-m=sn-m (n-m<n  n m) ⟩
-   suc (n - ( n - m ))  ≡⟨ cong (λ k → suc k ) (sym (n-n-m=m m≤n)) ⟩
-   suc m
-   ∎  ) where
-      open ≡-Reasoning
-
-0<s : {x : ℕ } → zero < suc x
-0<s {_} = s≤s z≤n 
-
 <-minus-0 : {x y z : ℕ } → z + x < z + y → x < y
 <-minus-0 {x} {suc _} {zero} lt = lt
 <-minus-0 {x} {y} {suc z} (s≤s lt) = <-minus-0 {x} {y} {z} lt
@@ -159,6 +217,16 @@
 x≤x+y {zero} {y} = z≤n
 x≤x+y {suc z} {y} = s≤s  (x≤x+y {z} {y})
 
+x≤y+x : {z y : ℕ } → z ≤ y + z
+x≤y+x {z} {y} = subst (λ k → z ≤ k ) (+-comm _ y ) x≤x+y
+
+x≤x+sy : {x y : ℕ} → x < x + suc y
+x≤x+sy {x} {y} = begin
+        suc x ≤⟨ x≤x+y ⟩
+        suc x + y ≡⟨ cong (λ k → k + y) (+-comm 1 x ) ⟩
+        (x + 1) + y ≡⟨ (+-assoc x 1 _) ⟩
+        x + suc y ∎  where open ≤-Reasoning
+
 <-plus : {x y z : ℕ } → x < y → x + z < y + z 
 <-plus {zero} {suc y} {z} (s≤s z≤n) = s≤s (subst (λ k → z ≤ k ) (+-comm z _ ) x≤x+y  )
 <-plus {suc x} {suc y} {z} (s≤s lt) = s≤s (<-plus {x} {y} {z} lt)
@@ -194,16 +262,88 @@
 <tos<s {zero} {suc y} (s≤s z≤n) = s≤s (s≤s z≤n)
 <tos<s {suc x} {suc y} (s≤s lt) = s≤s (<tos<s {x} {y} lt)
 
-≤to< : {x y  : ℕ } → x < y → x ≤ y 
-≤to< {zero} {suc y} (s≤s z≤n) = z≤n
-≤to< {suc x} {suc y} (s≤s lt) = s≤s (≤to< {x} {y}  lt)
+<to≤ : {x y  : ℕ } → x < y → x ≤ y 
+<to≤ {zero} {suc y} (s≤s z≤n) = z≤n
+<to≤ {suc x} {suc y} (s≤s lt) = s≤s (<to≤ {x} {y}  lt)
+
+<∨≤ : ( x y : ℕ ) →  (x < y ) ∨ (y ≤ x) 
+<∨≤ x y with <-cmp x y
+... | tri< a ¬b ¬c = case1 a
+... | tri≈ ¬a refl ¬c = case2 ≤-refl
+... | tri> ¬a ¬b c = case2 (<to≤ c)
+
+refl-≤ : {x : ℕ } → x ≤ x
+refl-≤ {zero} = z≤n
+refl-≤ {suc x} = s≤s (refl-≤ {x})
+
+refl-≤≡ : {x y : ℕ } → x ≡ y → x ≤ y
+refl-≤≡ refl = refl-≤ 
 
 x<y→≤ : {x y : ℕ } → x < y →  x ≤ suc y
 x<y→≤ {zero} {.(suc _)} (s≤s z≤n) = z≤n
 x<y→≤ {suc x} {suc y} (s≤s lt) = s≤s (x<y→≤ {x} {y} lt)
 
+≤→= : {i j : ℕ} → i ≤ j → j ≤ i → i ≡ j
+≤→= {0} {0} z≤n z≤n = refl
+≤→= {suc i} {suc j} (s≤s i<j) (s≤s j<i) = cong suc ( ≤→= {i} {j} i<j j<i )
+
+px≤x : {x  : ℕ } → pred x ≤ x 
+px≤x {zero} = refl-≤
+px≤x {suc x} = refl-≤s
+
+px≤py : {x y : ℕ } → x ≤ y → pred x  ≤ pred y 
+px≤py {zero} {zero} lt = refl-≤
+px≤py {zero} {suc y} lt = z≤n
+px≤py {suc x} {suc y} (s≤s lt) = lt 
+
+sx≤py→x≤y : {x y : ℕ } → suc x ≤ suc y → x  ≤ y 
+sx≤py→x≤y (s≤s lt) = lt
+
+sx<py→x<y : {x y : ℕ } → suc x < suc y → x  < y 
+sx<py→x<y (s≤s lt) = lt
+
+sx≤y→x≤y : {x y : ℕ } → suc x ≤ y → x  ≤ y 
+sx≤y→x≤y {zero} {suc y} (s≤s le) = z≤n
+sx≤y→x≤y {suc x} {suc y} (s≤s le) = s≤s (sx≤y→x≤y {x} {y} le)
+
+x<sy→x≤y : {x y : ℕ } → x < suc y → x  ≤ y 
+x<sy→x≤y {zero} {suc y} (s≤s le) = z≤n
+x<sy→x≤y {suc x} {suc y} (s≤s le) = s≤s (x<sy→x≤y {x} {y} le)
+x<sy→x≤y {zero} {zero} (s≤s z≤n) = ≤-refl
+
+x≤y→x<sy : {x y : ℕ } → x ≤ y → x < suc y 
+x≤y→x<sy {.zero} {y} z≤n = ≤-trans a<sa (s≤s z≤n)
+x≤y→x<sy {.(suc _)} {.(suc _)} (s≤s le) = s≤s ( x≤y→x<sy le) 
+
+sx≤y→x<y : {x y : ℕ } → suc x ≤ y → x < y 
+sx≤y→x<y {zero} {suc y} (s≤s le) = s≤s z≤n
+sx≤y→x<y {suc x} {suc y} (s≤s le) = s≤s ( sx≤y→x<y {x} {y} le )
+
 open import Data.Product
 
+i-j=0→i=j : {i j  : ℕ } → j ≤ i  → i - j ≡ 0 → i ≡ j
+i-j=0→i=j {zero} {zero} _ refl = refl
+i-j=0→i=j {zero} {suc j} () refl
+i-j=0→i=j {suc i} {zero} z≤n ()
+i-j=0→i=j {suc i} {suc j} (s≤s lt) eq = cong suc (i-j=0→i=j {i} {j} lt eq)
+
+m*n=0⇒m=0∨n=0 : {i j : ℕ} → i * j ≡ 0 → (i ≡ 0) ∨ ( j ≡ 0 )
+m*n=0⇒m=0∨n=0 {zero} {j} refl = case1 refl
+m*n=0⇒m=0∨n=0 {suc i} {zero} eq = case2 refl
+
+
+minus+1 : {x y  : ℕ } → y ≤ x  → suc (minus x y)  ≡ minus (suc x) y 
+minus+1 {zero} {zero} y≤x = refl
+minus+1 {suc x} {zero} y≤x = refl
+minus+1 {suc x} {suc y} (s≤s y≤x) = minus+1 {x} {y} y≤x 
+
+minus+yz : {x y z : ℕ } → z ≤ y  → x + minus y z  ≡ minus (x + y) z
+minus+yz {zero} {y} {z} _ = refl
+minus+yz {suc x} {y} {z} z≤y = begin
+         suc x + minus y z ≡⟨ cong suc ( minus+yz z≤y ) ⟩
+         suc (minus (x + y) z) ≡⟨ minus+1 {x + y} {z} (≤-trans z≤y (subst (λ g → y ≤ g) (+-comm y x) x≤x+y) ) ⟩
+         minus (suc x + y) z ∎  where open ≡-Reasoning
+
 minus<=0 : {x y : ℕ } → x ≤ y → minus x y ≡ 0
 minus<=0 {0} {zero} z≤n = refl
 minus<=0 {0} {suc y} z≤n = refl
@@ -213,6 +353,45 @@
 minus>0 {zero} {suc _} (s≤s z≤n) = s≤s z≤n
 minus>0 {suc x} {suc y} (s≤s lt) = minus>0 {x} {y} lt
 
+minus>0→x<y : {x y : ℕ } → 0 < minus y x  → x < y
+minus>0→x<y {x} {y} lt with <-cmp x y
+... | tri< a ¬b ¬c = a
+... | tri≈ ¬a refl ¬c = ⊥-elim ( nat-≡< (sym (minus<=0 {x} ≤-refl)) lt )
+... | tri> ¬a ¬b c = ⊥-elim ( nat-≡< (sym (minus<=0 {y} (≤-trans refl-≤s c ))) lt )
+
+minus+y-y : {x y : ℕ } → (x + y) - y  ≡ x
+minus+y-y {zero} {y} = minus<=0 {zero + y} {y} ≤-refl 
+minus+y-y {suc x} {y} = begin
+         (suc x + y) - y ≡⟨ sym (minus+1 {_} {y} x≤y+x) ⟩
+         suc ((x + y) - y) ≡⟨ cong suc (minus+y-y {x} {y}) ⟩
+         suc x ∎  where open ≡-Reasoning
+
+minus+yx-yz : {x y z : ℕ } → (y + x) - (y + z)  ≡ x - z
+minus+yx-yz {x} {zero} {z} = refl
+minus+yx-yz {x} {suc y} {z} = minus+yx-yz {x} {y} {z} 
+
+minus+xy-zy : {x y z : ℕ } → (x + y) - (z + y)  ≡ x - z
+minus+xy-zy {x} {y} {z} = subst₂ (λ j k → j - k ≡ x - z  ) (+-comm y x) (+-comm y z) (minus+yx-yz {x} {y} {z})
+
++cancel<l : (x z : ℕ ) {y : ℕ} → y + x < y + z → x < z
++cancel<l x z {zero} lt = lt
++cancel<l x z {suc y} (s≤s lt) = +cancel<l x z {y} lt
+
++cancel<r : (x z : ℕ ) {y : ℕ} → x + y < z + y → x < z
++cancel<r x z {y} lt = +cancel<l x z (subst₂ (λ j k → j < k ) (+-comm x _) (+-comm z _) lt ) 
+
+y-x<y : {x y : ℕ } → 0 < x → 0 < y  → y - x  <  y
+y-x<y {x} {y} 0<x 0<y with <-cmp x (suc y)
+... | tri< a ¬b ¬c = +cancel<r (y - x) _ ( begin
+         suc ((y - x) + x) ≡⟨ cong suc (minus+n {y} {x} a ) ⟩
+         suc y  ≡⟨ +-comm 1 _ ⟩
+         y + suc 0  ≤⟨ +-mono-≤ ≤-refl 0<x ⟩
+         y + x ∎ )  where open ≤-Reasoning
+... | tri≈ ¬a refl ¬c = subst ( λ k → k < y ) (sym (minus<=0 {y} {x} refl-≤s )) 0<y
+... | tri> ¬a ¬b c = subst ( λ k → k < y ) (sym (minus<=0 {y} {x} (≤-trans (≤-trans refl-≤s refl-≤s) c))) 0<y -- suc (suc y) ≤ x → y ≤ x
+
+open import Relation.Binary.Definitions
+
 distr-minus-* : {x y z : ℕ } → (minus x y) * z ≡ minus (x * z) (y * z) 
 distr-minus-* {x} {zero} {z} = refl
 distr-minus-* {x} {suc y} {z} with <-cmp x y
@@ -227,7 +406,7 @@
             le : x * z ≤ z + y * z
             le  = ≤-trans lemma (subst (λ k → y * z ≤ k ) (+-comm _ z ) (x≤x+y {y * z} {z} ) ) where
                lemma : x * z ≤ y * z
-               lemma = *≤ {x} {y} {z} (≤to< a)
+               lemma = *≤ {x} {y} {z} (<to≤ a)
 distr-minus-* {x} {suc y} {z} | tri≈ ¬a refl ¬c = begin
           minus x (suc y) * z
         ≡⟨ cong (λ k → k * z ) (minus<=0 {x} {suc y} refl-≤s ) ⟩
@@ -255,6 +434,13 @@
             lt : {x y z : ℕ } → suc y ≤ x → z + y * z ≤ x * z
             lt {x} {y} {z} le = *≤ le 
 
+distr-minus-*' : {z x y : ℕ } → z * (minus x y)  ≡ minus (z * x) (z * y) 
+distr-minus-*' {z} {x} {y} = begin
+        z * (minus x y) ≡⟨ *-comm _ (x - y) ⟩
+        (minus x y) * z ≡⟨ distr-minus-* {x} {y} {z} ⟩
+        minus (x * z) (y * z) ≡⟨ cong₂ (λ j k → j - k ) (*-comm x z ) (*-comm y z) ⟩
+        minus (z * x) (z * y) ∎  where open ≡-Reasoning
+
 minus- : {x y z : ℕ } → suc x > z + y → minus (minus x y) z ≡ minus x (y + z)
 minus- {x} {y} {z} gt = +m= {_} {_} {z} ( begin
            minus (minus x y) z + z
@@ -321,20 +507,278 @@
                       ∎   where open ≤-Reasoning
              open ≡-Reasoning
 
-open import Data.List
+x=y+z→x-z=y : {x y z : ℕ } → x ≡ y + z → x - z ≡ y
+x=y+z→x-z=y {x} {zero} {.x} refl = minus<=0 {x} {x} refl-≤ -- x ≡ suc (y + z) → (x ≡ y + z → x - z ≡ y)   → (x - z) ≡ suc y
+x=y+z→x-z=y {suc x} {suc y} {zero} eq = begin -- suc x ≡ suc (y + zero) → (suc x - zero) ≡ suc y
+       suc x - zero ≡⟨ refl ⟩
+       suc x  ≡⟨ eq ⟩
+       suc y + zero ≡⟨ +-comm _ zero ⟩
+       suc y ∎  where open ≡-Reasoning
+x=y+z→x-z=y {suc x} {suc y} {suc z} eq = x=y+z→x-z=y {x} {suc y} {z} ( begin
+       x ≡⟨ cong pred eq ⟩
+       pred (suc y + suc z) ≡⟨ +-comm _ (suc z)  ⟩
+       suc z + y ≡⟨ cong suc ( +-comm _ y ) ⟩
+       suc y + z ∎  ) where open ≡-Reasoning
+
+m*1=m : {m : ℕ } → m * 1 ≡ m
+m*1=m {zero} = refl
+m*1=m {suc m} = cong suc m*1=m
+
++-cancel-1 : (x y z : ℕ ) → x + y  ≡ x + z  → y ≡ z
++-cancel-1 zero y z eq = eq
++-cancel-1 (suc x) y z eq = +-cancel-1 x y z (cong pred eq )
+
++-cancel-0 : (x y z : ℕ ) → y + x ≡ z + x → y ≡ z
++-cancel-0 x y z eq = +-cancel-1 x y z (trans (+-comm x y) (trans eq (sym (+-comm x z)) ))
+
+*-cancel-left : {x y z : ℕ } → x > 0 → x * y ≡ x * z → y ≡ z
+*-cancel-left {suc x} {zero} {zero} lt eq = refl
+*-cancel-left {suc x} {zero} {suc z} lt eq = ⊥-elim ( nat-≡< eq (s≤s (begin
+  x * zero  ≡⟨ *-comm x _ ⟩ 
+  zero  ≤⟨ z≤n ⟩ 
+  z + x * suc z ∎ ))) where open ≤-Reasoning
+*-cancel-left {suc x} {suc y} {zero} lt eq = ⊥-elim ( nat-≡< (sym eq) (s≤s (begin
+  x * zero  ≡⟨ *-comm x _ ⟩ 
+  zero  ≤⟨ z≤n ⟩ 
+  _ ∎ ))) where open ≤-Reasoning
+*-cancel-left {suc x} {suc y} {suc z} lt eq with cong pred eq
+... | eq1 =  cong suc (*-cancel-left {suc x} {y} {z} lt (+-cancel-0 x _ _ (begin
+   y + x * y + x ≡⟨ +-assoc y _ _ ⟩ 
+   y + (x * y + x) ≡⟨ cong (λ k → y + (k + x)) (*-comm x _)  ⟩ 
+   y + (y * x + x) ≡⟨ cong (_+_ y) (+-comm _ x) ⟩ 
+   y + (x + y * x ) ≡⟨ refl ⟩ 
+   y + suc y * x ≡⟨ cong (_+_ y) (*-comm (suc y) _)  ⟩ 
+   y + x * suc y ≡⟨ eq1 ⟩ 
+   z + x * suc z ≡⟨ refl ⟩ 
+   _ ≡⟨ sym ( cong (_+_ z) (*-comm (suc z) _) ) ⟩ 
+   _ ≡⟨ sym ( cong (_+_ z) (+-comm _ x)) ⟩ 
+   z + (z * x + x) ≡⟨ sym ( cong (λ k → z + (k + x)) (*-comm x _) ) ⟩ 
+   z + (x * z + x) ≡⟨ sym ( +-assoc z _ _) ⟩ 
+   z + x * z + x  ∎ ))) where open ≡-Reasoning
+
+record Finduction {n m : Level} (P : Set n ) (Q : P → Set m ) (f : P → ℕ) : Set  (n Level.⊔ m) where
+  field
+    fzero   : {p : P} → f p ≡ zero → Q p
+    pnext : (p : P ) → P
+    decline : {p : P} → 0 < f p  → f (pnext p) < f p
+    ind : {p : P} → Q (pnext p) → Q p
+
+y<sx→y≤x : {x y : ℕ} → y < suc x → y ≤ x
+y<sx→y≤x (s≤s lt) = lt 
+
+fi0 : (x : ℕ) → x ≤ zero → x ≡ zero
+fi0 .0 z≤n = refl
 
-ℕL-inject : {h h1 : ℕ } {x y : List ℕ } → h ∷ x ≡ h1 ∷ y → h ≡ h1
-ℕL-inject refl = refl
+f-induction : {n m : Level} {P : Set n } → {Q : P → Set m }
+  → (f : P → ℕ) 
+  → Finduction P Q f
+  → (p : P ) → Q p
+f-induction {n} {m} {P} {Q} f I p with <-cmp 0 (f p)
+... | tri> ¬a ¬b ()
+... | tri≈ ¬a b ¬c = Finduction.fzero I (sym b) 
+... | tri< lt _ _ = f-induction0 p (f p) (<to≤ (Finduction.decline I lt)) where 
+   f-induction0 : (p : P) → (x : ℕ) → (f (Finduction.pnext I p)) ≤ x → Q p
+   f-induction0 p zero le = Finduction.ind I (Finduction.fzero I (fi0 _ le)) 
+   f-induction0 p (suc x) le with <-cmp (f (Finduction.pnext I p)) (suc x)
+   ... | tri< (s≤s a) ¬b ¬c = f-induction0 p x a 
+   ... | tri≈ ¬a b ¬c = Finduction.ind I (f-induction0 (Finduction.pnext I p) x (y<sx→y≤x f1)) where
+       f1 : f (Finduction.pnext I (Finduction.pnext I p)) < suc x
+       f1 = subst (λ k → f (Finduction.pnext I (Finduction.pnext I p)) < k ) b ( Finduction.decline I {Finduction.pnext I p}
+         (subst (λ k → 0 < k ) (sym b) (s≤s z≤n ) ))
+   ... | tri> ¬a ¬b c = ⊥-elim ( nat-≤> le c ) 
+
+
+record Ninduction {n m : Level} (P : Set n ) (Q : P → Set m ) (f : P → ℕ) : Set  (n Level.⊔ m) where
+  field
+    pnext : (p : P ) → P
+    fzero   : {p : P} → f (pnext p) ≡ zero → Q p
+    decline : {p : P} → 0 < f p  → f (pnext p) < f p
+    ind : {p : P} → Q (pnext p) → Q p
+
+s≤s→≤ : { i j : ℕ} → suc i ≤ suc j → i ≤ j
+s≤s→≤ (s≤s lt) = lt
 
-ℕL-inject-t : {h h1 : ℕ } {x y : List ℕ } → h ∷ x ≡ h1 ∷ y → x ≡ y
-ℕL-inject-t refl = refl
+n-induction : {n m : Level} {P : Set n } → {Q : P → Set m }
+  → (f : P → ℕ) 
+  → Ninduction P Q f
+  → (p : P ) → Q p
+n-induction {n} {m} {P} {Q} f I p  = f-induction0 p (f (Ninduction.pnext I p)) ≤-refl where 
+   f-induction0 : (p : P) → (x : ℕ) → (f (Ninduction.pnext I p)) ≤ x  →  Q p
+   f-induction0 p zero lt = Ninduction.fzero I {p} (fi0 _ lt) 
+   f-induction0 p (suc x) le with <-cmp (f (Ninduction.pnext I p)) (suc x) 
+   ... | tri< (s≤s a)  ¬b ¬c = f-induction0 p x a
+   ... | tri≈ ¬a b ¬c = Ninduction.ind I (f-induction0 (Ninduction.pnext I p) x (s≤s→≤ nle) ) where
+      f>0 :  0 < f (Ninduction.pnext I p)
+      f>0 = subst (λ k → 0 < k ) (sym b) ( s≤s z≤n ) 
+      nle : suc (f (Ninduction.pnext I (Ninduction.pnext I p))) ≤ suc x
+      nle = subst (λ k → suc (f (Ninduction.pnext I (Ninduction.pnext I p))) ≤ k) b (Ninduction.decline I {Ninduction.pnext I p} f>0 ) 
+   ... | tri> ¬a ¬b c = ⊥-elim ( nat-≤> le c )  
+
+
+record Factor (n m : ℕ ) : Set where
+   field 
+      factor : ℕ
+      remain : ℕ
+      is-factor : factor * n + remain ≡ m
+
+record Dividable (n m : ℕ ) : Set where
+   field 
+      factor : ℕ
+      is-factor : factor * n + 0 ≡ m 
+
+open Factor
+
+DtoF : {n m : ℕ} → Dividable n m → Factor n m
+DtoF {n} {m} record { factor = f ; is-factor = fa } = record { factor = f ; remain = 0 ; is-factor = fa }
+
+FtoD : {n m : ℕ} → (fc : Factor n m) → remain fc ≡ 0 → Dividable n m 
+FtoD {n} {m} record { factor = f ; remain = r ; is-factor = fa } refl = record { factor = f ; is-factor = fa }
+
+--divdable^2 : ( n k : ℕ ) → Dividable k ( n * n ) → Dividable k n
+--divdable^2 n k dn2 = {!!}
 
-ℕL-eq? : (x y : List ℕ ) → Dec (x ≡ y )
-ℕL-eq? [] [] = yes refl
-ℕL-eq? [] (x ∷ y) = no (λ ())
-ℕL-eq? (x ∷ x₁) [] = no (λ ())
-ℕL-eq? (h ∷ x) (h1 ∷ y) with h ≟ h1 | ℕL-eq? x y
-... | yes y1 | yes y2 = yes ( cong₂ (λ j k → j ∷ k ) y1 y2 )
-... | yes y1 | no n = no (λ e → n (ℕL-inject-t e))
-... | no n  | t = no (λ e → n (ℕL-inject e)) 
+decf : { n k : ℕ } → ( x : Factor k (suc n) ) → Factor k n
+decf {n} {k} record { factor = f ; remain = r ; is-factor = fa } = 
+ decf1 {n} {k} f r fa where
+  decf1 : { n k : ℕ } → (f r : ℕ) → (f * k + r ≡ suc n)  → Factor k n 
+  decf1 {n} {k} f (suc r) fa  =  -- this case must be the first
+     record { factor = f ; remain = r ; is-factor = ( begin -- fa : f * k + suc r ≡ suc n
+        f * k + r ≡⟨ cong pred ( begin
+          suc ( f * k + r ) ≡⟨ +-comm _ r ⟩
+          r + suc (f * k)  ≡⟨ sym (+-assoc r 1 _) ⟩
+          (r + 1) + f * k ≡⟨ cong (λ t → t + f * k ) (+-comm r 1) ⟩
+          (suc r ) + f * k ≡⟨ +-comm (suc r) _ ⟩
+          f * k + suc r  ≡⟨ fa ⟩
+          suc n ∎ ) ⟩ 
+        n ∎ ) }  where open ≡-Reasoning
+  decf1 {n} {zero} (suc f) zero fa  = ⊥-elim ( nat-≡< fa (
+        begin suc (suc f * zero + zero) ≡⟨ cong suc (+-comm _ zero)  ⟩
+        suc (f * 0) ≡⟨ cong suc (*-comm f zero)  ⟩
+        suc zero ≤⟨ s≤s z≤n ⟩
+        suc n ∎ )) where open ≤-Reasoning
+  decf1 {n} {suc k} (suc f) zero fa  = 
+     record { factor = f ; remain = k ; is-factor = ( begin -- fa : suc (k + f * suc k + zero) ≡ suc n
+        f * suc k + k ≡⟨ +-comm _ k ⟩
+        k + f * suc k ≡⟨ +-comm zero _ ⟩
+        (k + f * suc k) + zero  ≡⟨ cong pred fa ⟩
+        n ∎ ) }  where open ≡-Reasoning
+
+div0 :  {k : ℕ} → Dividable k 0
+div0 {k} = record { factor = 0; is-factor = refl }
+
+div= :  {k : ℕ} → Dividable k k
+div= {k} = record { factor = 1; is-factor = ( begin
+        k + 0 * k + 0  ≡⟨ trans ( +-comm _ 0) ( +-comm _ 0) ⟩
+        k ∎ ) }  where open ≡-Reasoning
+
+div1 : { k : ℕ } → k > 1 →  ¬  Dividable k 1
+div1 {k} k>1 record { factor = (suc f) ; is-factor = fa } = ⊥-elim ( nat-≡< (sym fa) ( begin
+    2 ≤⟨ k>1 ⟩
+    k ≡⟨ +-comm 0 _ ⟩
+    k + 0 ≡⟨ refl  ⟩
+    1 * k ≤⟨ *-mono-≤ {1} {suc f} (s≤s z≤n ) ≤-refl ⟩
+    suc f * k ≡⟨ +-comm 0 _ ⟩
+    suc f * k + 0 ∎  )) where open ≤-Reasoning  
+
+div+div : { i j k : ℕ } →  Dividable k i →  Dividable k j → Dividable k (i + j) ∧ Dividable k (j + i)
+div+div {i} {j} {k} di dj = ⟪ div+div1 , subst (λ g → Dividable k g) (+-comm i j) div+div1 ⟫ where
+      fki = Dividable.factor di
+      fkj = Dividable.factor dj
+      div+div1 : Dividable k (i + j)
+      div+div1 = record { factor = fki + fkj  ; is-factor = ( begin 
+          (fki + fkj) * k + 0 ≡⟨ +-comm _ 0 ⟩
+          (fki + fkj) * k  ≡⟨ *-distribʳ-+ k fki _ ⟩
+          fki * k + fkj * k  ≡⟨ cong₂ ( λ i j → i + j ) (+-comm 0 (fki * k)) (+-comm 0 (fkj * k)) ⟩
+          (fki * k + 0) + (fkj * k + 0) ≡⟨ cong₂ ( λ i j → i + j ) (Dividable.is-factor di) (Dividable.is-factor dj) ⟩
+          i + j  ∎ ) } where
+             open ≡-Reasoning  
+
+div-div : { i j k : ℕ } → k > 1 →  Dividable k i →  Dividable k j → Dividable k (i - j) ∧ Dividable k (j - i)
+div-div {i} {j} {k} k>1 di dj = ⟪ div-div1 di dj , div-div1 dj di ⟫ where
+      div-div1 : {i j : ℕ } → Dividable k i →  Dividable k j → Dividable k (i - j)
+      div-div1 {i} {j} di dj = record { factor = fki - fkj  ; is-factor = ( begin 
+          (fki - fkj) * k + 0 ≡⟨ +-comm _ 0 ⟩
+          (fki - fkj) * k  ≡⟨ distr-minus-* {fki} {fkj}  ⟩
+          (fki * k) - (fkj * k)  ≡⟨ cong₂ ( λ i j → i - j ) (+-comm 0 (fki * k)) (+-comm 0 (fkj * k)) ⟩
+          (fki * k + 0) - (fkj * k + 0) ≡⟨ cong₂ ( λ i j → i - j ) (Dividable.is-factor di) (Dividable.is-factor dj) ⟩
+          i - j  ∎ ) } where
+             open ≡-Reasoning  
+             fki = Dividable.factor di
+             fkj = Dividable.factor dj
+
+open _∧_
 
+div+1 : { i k : ℕ } → k > 1 →  Dividable k i →  ¬ Dividable k (suc i)  
+div+1 {i} {k} k>1 d d1 = div1 k>1 div+11 where
+   div+11 : Dividable k 1
+   div+11 = subst (λ g → Dividable k g) (minus+y-y {1} {i} ) ( proj2 (div-div k>1 d d1  ) )
+
+div<k : { m k : ℕ } → k > 1 → m > 0 →  m < k →  ¬ Dividable k m
+div<k {m} {k} k>1 m>0 m<k d = ⊥-elim ( nat-≤> (div<k1 (Dividable.factor d) (Dividable.is-factor d)) m<k ) where
+    div<k1 : (f : ℕ ) → f * k + 0 ≡ m → k ≤ m
+    div<k1 zero eq = ⊥-elim (nat-≡< eq m>0 )
+    div<k1 (suc f) eq = begin
+          k ≤⟨ x≤x+y ⟩
+          k + (f * k + 0) ≡⟨ sym (+-assoc k _ _) ⟩
+          k + f * k + 0 ≡⟨ eq ⟩
+          m ∎  where open ≤-Reasoning  
+
+0<factor : { m k : ℕ } → k > 0 → m > 0 →  (d :  Dividable k m ) → Dividable.factor d > 0
+0<factor {m} {k} k>0 m>0 d with Dividable.factor d | inspect Dividable.factor d 
+... | zero | record { eq = eq1 } = ⊥-elim ( nat-≡< ff1 m>0 ) where
+    ff1 : 0 ≡ m 
+    ff1 = begin
+          0 ≡⟨⟩
+          0 * k + 0 ≡⟨ cong  (λ j → j * k + 0) (sym eq1) ⟩
+          Dividable.factor d * k + 0 ≡⟨ Dividable.is-factor d  ⟩
+          m ∎  where open ≡-Reasoning  
+... | suc t | _ = s≤s z≤n 
+
+div→k≤m : { m k : ℕ } → k > 1 → m > 0 →  Dividable k m → m ≥ k
+div→k≤m {m} {k} k>1 m>0 d with <-cmp m k
+... | tri< a ¬b ¬c = ⊥-elim ( div<k k>1 m>0 a d )
+... | tri≈ ¬a refl ¬c = ≤-refl
+... | tri> ¬a ¬b c = <to≤ c
+
+div1*k+0=k : {k : ℕ } → 1 * k + 0 ≡ k
+div1*k+0=k {k} =  begin
+   1 * k + 0 ≡⟨ cong (λ g → g + 0) (+-comm _ 0) ⟩
+   k + 0 ≡⟨ +-comm _ 0 ⟩
+   k  ∎ where open ≡-Reasoning
+
+decD : {k m : ℕ} → k > 1 → Dec (Dividable k m )
+decD {k} {m} k>1 = n-induction {_} {_} {ℕ} {λ m → Dec (Dividable k m ) } F I m where
+        F : ℕ → ℕ
+        F m = m
+        F0 : ( m : ℕ ) → F (m - k) ≡ 0 →  Dec  (Dividable k m  )
+        F0 0 eq = yes record { factor = 0 ; is-factor = refl }
+        F0 (suc m) eq with <-cmp k (suc m)
+        ... | tri< a ¬b ¬c = yes  record { factor = 1 ; is-factor =
+            subst (λ g → 1 * k + 0 ≡ g ) (sym (i-j=0→i=j (<to≤ a) eq )) div1*k+0=k }  -- (suc m - k) ≡ 0 → k ≡ suc m, k ≤ suc m
+        ... | tri≈ ¬a refl ¬c =  yes   record { factor = 1 ; is-factor = div1*k+0=k } 
+        ... | tri> ¬a ¬b c = no ( λ d →  ⊥-elim (div<k k>1 (s≤s z≤n ) c d) )
+        decl : {m  : ℕ } → 0 < m → m - k < m
+        decl {m} 0<m = y-x<y (<-trans a<sa k>1 ) 0<m 
+        ind : (p : ℕ ) → Dec (Dividable k (p - k) ) → Dec (Dividable k p )
+        ind p (yes y) with <-cmp p k
+        ... | tri≈ ¬a refl ¬c = yes (subst (λ g → Dividable k g) (minus+n ≤-refl ) (proj1 ( div+div y div= ))) 
+        ... | tri> ¬a ¬b k<p  = yes (subst (λ g → Dividable k g) (minus+n (<-trans k<p a<sa)) (proj1 ( div+div y div= ))) 
+        ... | tri< a ¬b ¬c with <-cmp p 0
+        ... | tri≈ ¬a refl ¬c₁ = yes div0
+        ... | tri> ¬a ¬b₁ c = no (λ d → not-div p (Dividable.factor d) a c (Dividable.is-factor d) ) where
+            not-div : (p f : ℕ) → p < k  → 0 < p → f * k + 0 ≡ p → ⊥
+            not-div (suc p) (suc f) p<k 0<p eq = nat-≡< (sym eq) ( begin -- ≤-trans p<k {!!}) -- suc p ≤ k
+              suc (suc p) ≤⟨ p<k ⟩
+              k ≤⟨ x≤x+y  ⟩
+              k + (f * k + 0) ≡⟨ sym (+-assoc k _ _) ⟩
+              suc f * k + 0 ∎  ) where open ≤-Reasoning  
+        ind p (no n) = no (λ d → n (proj1 (div-div k>1 d div=))  ) 
+        I : Ninduction ℕ  _  F
+        I = record {
+              pnext = λ p → p - k
+            ; fzero = λ {m} eq → F0 m eq
+            ; decline = λ {m} lt → decl lt 
+            ; ind = λ {p} prev → ind p prev
+          } 
+
+
--- a/src/sym5h.agda	Fri Sep 15 23:36:43 2023 +0900
+++ b/src/sym5h.agda	Sat Sep 16 11:40:13 2023 +0900
@@ -67,6 +67,14 @@
            G→3 :  RawGroup.Carrier (GR (SGroup G isSub)) → Permutation 3 3
            is-sym3 : IsGroupIsomorphism (GR (SGroup G isSub)) (GR (Symmetric 3)) G→3
 
+     record sym3elms (abc : Permutation 3 3) : Set where 
+        field
+           sa sb sc : ℕ
+           abc=sym3 : plist0 abc ≡ (sa ∷ sb ∷ sc ∷ [])
+
+     sym3→elm : (abc : Permutation 3 3) → sym3elms abc 
+     sym3→elm abc = record { sa = _ ; sb = _ ; sc = _ ; abc=sym3 = refl }   
+
      open _=p=_
      -- Symmetric 3 is a normal subgroup of Symmetric 5
      s00 : HaveSym3 (Symmetric 5) 
@@ -133,6 +141,9 @@
                    ; injective = λ eq → ? }
            ;  surjective = λ nx → s16 nx , s17 nx  }
         } where
+           -- [ dba , aec ] = (abd)(cea)(dba)(aec) = abc
+           --    dba = (dc)(cba)(cd) = (dc)(abc)⁻¹(cd) 
+           --    aec = (eb)(abc) (be)
            sym3 : HaveSym3 (SGroup _ (NormalSubGroup.Psub (CommNormal (Symmetric 5) i))) 
            sym3 = s01 i
            s10 : Nelm (Symmetric 5) (NormalSubGroup.Psub (CommNormal (Symmetric 5) (suc i))) → Set
@@ -143,14 +154,41 @@
            s15 record { elm = record { elm = elm ; Pelm = ic } ; Pelm = Pelm } = shrink (shrink elm (proj₁ Pelm)) ? 
            s16 : Permutation 3 3  → Nelm (SGroup (Symmetric 5) (NormalSubGroup.Psub (CommNormal (Symmetric 5) (suc i)))) sub01
            s16 abc = record { elm = record { elm = ? ; Pelm = ? } ; Pelm = ? } where
+              ABC : sym3elms abc
+              ABC = sym3→elm abc
+              sa = sym3elms.sa ABC
+              sb = sym3elms.sb ABC
+              sc = sym3elms.sc ABC
+              dc : Permutation 5 5
+              dc = ?
+              eb : Permutation 5 5
+              eb = ?
               dba : Permutation 5 5
-              dba = ?
+              dba = dc ∘ₚ (pprep (pprep abc)) ∘ₚ pinv dc
               aec : Permutation 5 5
-              aec = ?
-              Cdba : deriving (Symmetric 5) i ?
-              Cdba = Pcomm _ {pprep (pprep abc)} {?} i ?
-              Caec : deriving (Symmetric 5) i ?
-              Caec = Pcomm _ {pinv (pprep (pprep abc))} {?} i ?
+              aec = eb ∘ₚ (pprep (pprep abc)) ∘ₚ pinv eb
+              Cdba : deriving (Symmetric 5) i dba
+              Cdba = Pcomm _ {pprep (pprep abc)} {dc} i s26 where
+                  s22 : Group.Carrier (SGroup _ (HaveSym3.isSub sym3))
+                  s22 = proj₁ (IsGroupIsomorphism.surjective (HaveSym3.is-sym3 sym3) abc)
+                  s23 : HaveSym3.G→3 sym3 s22 =p= abc
+                  s23 = proj₂ (IsGroupIsomorphism.surjective (HaveSym3.is-sym3 sym3) abc)
+                  s24 : deriving (Symmetric 5) i (pprep (pprep abc))
+                  s24 with Nelm.Pelm (Nelm.elm s22 )
+                  ... | t = ?
+                  s25 : SubGroup.P (NormalSubGroup.Psub (CommNormal (Symmetric 5) i)) ?
+                  s25 = ?
+                  s26 : deriving (Symmetric 5) i (pprep (pprep abc))
+                  s26 = ?
+                  -- s22 is finitely generated element from commutor 
+                  -- what we need is a Commutator not iCommutator
+                  -- so this method is no good
+                  s27 : iCommutator (Symmetric 5) i (Nelm.elm (Nelm.elm s22))
+                  s27 = Nelm.Pelm (Nelm.elm s22 )
+                  s28 : SubGroup.P (HaveSym3.isSub sym3) (Nelm.elm s22)
+                  s28 = Nelm.Pelm s22
+              Caec : deriving (Symmetric 5) i aec
+              Caec = Pcomm _ {pinv (pprep (pprep abc))} {eb} i ?
               s18 :  iCommutator (Symmetric 5) (suc i) (pprep (pprep abc))
               s18 = iunit (ccong ? ( comm Cdba Caec ))
            s17 : (abc : Permutation 3 3 ) →  s15 (s16 abc) =p= abc