Question

I need to split a list into a list of all possible tuples, but I’m unsure of how to do so.

For example:

pairs ["cat","dog","mouse"]

should result in:

[("cat","dog"), ("cat","mouse"), ("dog","cat"), ("dog","mouse"), ("mouse","cat"), ("mouse","dog")]

I was able to form the first two, but am unsure of how to get the rest.

Here’s what I have so far:

pairs :: [a] -> [(a,a)]
pairs (x:xs) = [(m,n) | m <- [x], n <- xs]

Answer 1

You can use a list comprehension:

allpairs :: Eq a => [a] -> [(a,a)]
allpairs xs = [ (x1,x2) | x1 <- xs, x2 <- xs, x1 /= x2 ]