OK, you have the split function, and you have the merge function, and now you have to define the
msort function. First write down the base cases (there are two, as you mention), which should be
obvious. Then consider the remaining case. Let's say you split the list into two parts. Then what
would you do?
Mike
PR Stanley wrote:
I'm not sure. We start with one list and also, perhaps I should have
mentioned that I have a merge function which takes two sorted lists with
similar, now, what do they call it, similar orientation? and merges them
into one sorted list.
e.g. merge [1, 4,] [2, 3]
[1,2,3,4]
Cheers, Paul
At 04:02 14/09/2007, you wrote:
Define a merge function that merges two sorted lists into a sorted
list containing all the elements of the two lists. Then define the
msort function, which will be recursive.
Mike
PR Stanley wrote:
Hi
Taken from chapter 6, section 8 of the Hutton book on programming in
Haskell:
5. Using merge, define a recursive function
msort :: (Ord a) => [a] -> [a]
that implements merge sort, in which the empty list and singleton
lists are already sorted, and any other list is sorted by merging
together the two lists that result from sorting the two halves of the
list separately. :
Hint: first define a function
¬halve :: [a] -> [([a], [a])]
¬that splits a list into two halves whose length differs by at most one.
Create a halve function - okay, that's fairly straightforward.
The rest, I'm afraid, is a little obscure. I'm not looking for the
solution; I'd like to work that out for meself. However, I'd really
appreciate some clues as to the general structure of the algorithm.
Much obliged,
Paul
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