blob: 3ebb6ceca14dde41e54a63066fe6663ea6f42b23 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
||this is a problem described by Dijkstra in his book, A Discipline of
||Programming, and attributed by him to Dr Hamming, of Bell Labs.
||Print in ascending order all numbers of the form
|| 2**a.3**b.5**c a,b,c all >=0
||the solution here is based on a method using communicating processes.
||ham is the list of numbers, to see them, say
|| ham
||hit control-C (interrupt) when you have seen enough!
ham = 1 : foldr1 merge [mult 2 ham, mult 3 ham, mult 5 ham]
where
mult n x = [n*a|a<-x]
merge (a:x) (b:y) = a : merge x y, if a=b
= a : merge x (b:y), if a<b
= b : merge (a:x) y, if a>b
||Note that there is a function called `merge' in the standard
||environment, but unlike the one defined above it does not remove
||duplicates from the lists being merged.
|
