diff options
Diffstat (limited to 'fp1/week6/mart/BewijsMapFlatten.icl')
| -rw-r--r-- | fp1/week6/mart/BewijsMapFlatten.icl | 97 |
1 files changed, 0 insertions, 97 deletions
diff --git a/fp1/week6/mart/BewijsMapFlatten.icl b/fp1/week6/mart/BewijsMapFlatten.icl deleted file mode 100644 index 59fa5bc..0000000 --- a/fp1/week6/mart/BewijsMapFlatten.icl +++ /dev/null @@ -1,97 +0,0 @@ -Zij gegeven:
-
-(++) :: [a] [a] -> [a]
-(++) [] xs = xs (1)
-(++) [y:ys] xs = [y : ys ++ xs] (2)
-
-map :: (a -> b) [a] -> [b]
-map f [] = [] (3)
-map f [x:xs] = [f x : map f xs] (4)
-
-flatten :: [[a]] -> [a]
-flatten [] = [] (5)
-flatten [x:xs] = x ++ (flatten xs) (6)
-
-1.
-Te bewijzen:
- voor iedere functie f, eindige lijst as en bs:
-
- map f (as ++ bs) = (map f as) ++ (map f bs)
-
-Bewijs:
- met inductie naar de lengte van as.
-
- Basis:
- aanname: as = [].
-
- map f ([] ++ bs) = (map f []) ++ (map f bs) basis
- ********
- => map f (bs) = (map f []) ++ (map f bs) (1)
- ********
- => map f (bs) = [] ++ (map f bs) (3)
- ****************
- => map f bs = map f bs (1)
-
- Inductiestap:
- aanname: stelling geldt voor zekere as, ofwel:
- map f (as ++ bs) = (map f as) ++ (map f bs) (IH)
-
- Te bewijzen: stelling geldt ook voor as, ofwel:
- map f ([a:as] ++ bs) = (map f [a:as]) ++ (map f bs)
-
- map f ([a:as] ++ bs) = (map f [a:as]) ++ (map f bs) basis
- ************
- => map f [a:as ++ bs] = (map f [a:as]) ++ (map f bs) (2)
- ******************
- => [f a : map f (as ++ bs)] = (map f [a:as]) ++ (map f bs) (4)
- ************
- => [f a : map f (as ++ bs)] = [f a : map f as] ++ (map f bs) (4)
- ****************************
- => [f a : map f (as ++ bs)] = [f a : (map f as) ++ (map f bs)] (4)
- **************** ************************
- => map f (as ++ bs) = (map f as) ++ (map f bs) (IH)
-
- Dus: basis + inductiestap => stelling bewezen.
-
-2.
-Te bewijzen:
- voor iedere functie f, voor iedere eindige lijst xs:
-
- flatten (map (map f) xs) = map f (flatten xs)
-
-Bewijs:
- met inductio van de lengte van xs
-
- Basis:
- aanname: xs = [].
-
- flatten (map (map f) []) = map f (flatten []) basis
- **************
- = flatten [] = map f (flatten []) (3)
- **********
- = flatten [] = map f [] (5)
- **********
- = [] = map f [] (5)
- *****
- = [] = [] (3)
-
- Inductiestap:
- aanname: stelling geldt voor zekere xs, ofwel:
- flatten (map (map f) xs) = map f (flatten xs)
-
- Te bewijzen: stelling geldt ook voor xs, ofwel:
- flatten (map (map f) [x:xs]) = map f (flatten [x:xs])
-
- flatten (map (map f) [x:xs]) = map f (flatten [x:xs]) basis
- ******************
- => flatten [map f x: map (map f) xs] = map f (flatten [x:xs]) (4)
- *********************************
- => (map f x) ++ (flatten (map (map f) xs)) = map f (flatten [x:xs]) (6)
- **************
- => (map f x) ++ (flatten (map (map f) xs)) = map f (x ++ (flatten xs)) (6)
- *************************
- => (map f x) ++ (flatten (map (map f) xs)) = (map f x) ++ (map f (flatten xs)) (9.4.1)
- ************************ ****************
- => flatten (map (map f) xs) = map f (flatten xs) (IH)
-
- Dus: basis + inductiestap => stelling bewezen.
|