Re: [Haskell-beginners] Why does this list comprehension return an empty list?

On Tue, Jul 23, 2013 at 3:53 PM, Costello, Roger L. wrote:

Also, how would I modify this:

[(a,b) | a <- f xs, b <- g xs]

so that it produces this:

[("a",[])]

Try: [(a,b) | a <- f xs | b <- g xs] Note the 2nd parallel bar. You may have to enable a Parallel List Comprehension pragma or somesuch. Everyone else has given great explanations about your curious definitions of f and g and why the original does what it does. Well worth looking into. -- Kim-Ee