Editing Miranda (programming language) (section)

==Sample code==

The following Miranda script determines the set of all subsets of a set of numbers

<syntaxhighlight lang="haskell">
 subsets []     = [[]]
 subsets (x:xs) = [[x] ++ y | y <- ys] ++ ys
                  where ys = subsets xs
</syntaxhighlight>

and this is a literate script for a function <code>primes</code>
which gives the list of all prime numbers

<syntaxhighlight lang="text">
> || The infinite list of all prime numbers.

The list of potential prime numbers starts as all integers from 2 onwards;
as each prime is returned, all the following numbers that can exactly be
divided by it are filtered out of the list of candidates.

> primes = sieve [2..]
> sieve (p:x) = p : sieve [n | n <- x; n mod p ~= 0]
</syntaxhighlight>

Here, we have some more examples

<syntaxhighlight lang="haskell">
max2 :: num -> num -> num
max2 a b = a, if a>b
         = b, otherwise

max3 :: num -> num -> num -> num
max3 a b c = max2 (max2 a b) (max2 a c)

multiply :: num -> num -> num
multiply 0 b = 0
multiply a b = b + (multiply (a-1) b)

fak :: num -> num
fak 0 = 1
fak n = n * fak (n-1)



itemnumber::[*]->num
itemnumber [] = 0
itemnumber (a:x) = 1 + itemnumber x

weekday::= Mo|Tu|We|Th|Fr|Sa|Su

isWorkDay :: weekday -> bool
isWorkDay Sa = False
isWorkDay Su = False
isWorkDay anyday = True


tree * ::= E| N (tree *) * (tree *)

nodecount :: tree * -> num
nodecount E = 0
nodecount (N l w r) = nodecount l + 1 + nodecount r

emptycount :: tree * -> num
emptycount E = 1
emptycount (N l w r) = emptycount l + emptycount r



treeExample = N ( N (N E 1 E) 3 (N E 4 E)) 5 (N (N E 6 E) 8 (N E 9 E))
weekdayTree = N ( N (N E Mo E) Tu (N E We E)) Th (N (N E Fr E) Sa (N E Su))

insert :: * -> stree * -> stree *
insert x E = N E x E
insert x (N l w E) = N l w x
insert x (N E w r) = N x w r
insert x (N l w r) = insert x l , if x <w
                   = insert x r , otherwise

list2searchtree :: [*] -> tree *
list2searchtree [] = E
list2searchtree [x] = N E x E
list2searchtree (x:xs) = insert x (list2searchtree xs)

maxel :: tree * -> *
maxel E = error "empty"
maxel (N l w E) = w
maxel (N l w r) = maxel r

minel :: tree * -> *
minel E = error "empty"
minel (N E w r) = w
minel (N l w r) = minel l

||Traversing: going through values of tree, putting them in list

preorder,inorder,postorder :: tree * -> [*]
inorder E = []
inorder N l w r = inorder l ++ [w] ++ inorder r

preorder E = []
preorder N l w r = [w] ++ preorder l ++ preorder r

postorder E = []
postorder N l w r = postorder l ++ postorder r ++ [w]

height :: tree * -> num
height E = 0
height (N l w r) = 1 + max2 (height l) (height r)




amount :: num -> num
amount x = x ,if x >= 0
amount x = x*(-1), otherwise


and :: bool -> bool -> bool
and True True = True
and x y = False

|| A AVL-Tree is a tree where the difference between the child nodes is not higher than 1
|| i still have to test this

isAvl :: tree * -> bool
isAvl E = True
isAvl (N l w r) = and (isAvl l) (isAvl r), if amount ((nodecount l) - (nodecount r)) < 2
                = False, otherwise




delete :: * -> tree * -> tree *
delete x E = E
delete x (N E x E) = E
delete x (N E x r) = N E (minel r) (delete (minel r) r)
delete x (N l x r) = N (delete (maxel l) l) (maxel l) r
delete x (N l w r) = N (delete x l) w (delete x r)

</syntaxhighlight>