Generating sorted list of all possible coprimes

Question

I need to generate infinite sorted list of all coprimes. The first element in each pair must be less than the second. The sorting must be done in ascending order -- by the sum o

Answer 1

I need to generate infinite sorted list of all coprimes. The first element in each pair must be less than the second. The sorting must be done in ascending order -- by the sum of pair's elements; and if two sums are equal, then by the pair's first element.

So, we generate ascending pairs of sum and first element, and keep only the coprimes. Easy cheesy!

[ (first, second)
| sum <- [3..]
, first <- [2..sum `div` 2]
, let second = sum-first
, gcd first second == 1
]