On Fri, Aug 3, 2012 at 11:34 PM, Matthew
I'm a somewhat experienced coder but I am relatively new to Haskell. I've got a question about whether a usage of do notation is idiomatic, or whether it's better to use pattern matching.
I've got two functions which take an input and return Maybe SomeType. If either returns Nothing, I also want to return Nothing. If they both return something, then I'll return something unrelated.
With do notation, I can write something like this:
do foo <- callFoo x bar <- callBar x return (baz)
Alternatively, there's a straightforward pattern match. After binding foo, bar in a couple of where clauses:
case (foo,bar) of (Just x, Just y) -> baz _ -> Nothing
So which approach is more idiomatic, do you think?
The short answer is to write a "one liner" using (>>=) and (>>), unless you need to bind more than one value to a variable. In that case, you should use an applicative interface, if available and otherwise possible, and finally do-notation.