[Haskell-cafe] do vs. pattern matching
wonderzombie at gmail.com
Sun Aug 5 02:35:25 CEST 2012
On Sat, Aug 4, 2012 at 7:05 AM, Alexander Solla <alex.solla at gmail.com> wrote:
> On Fri, Aug 3, 2012 at 11:34 PM, Matthew <wonderzombie at gmail.com> wrote:
>> 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:
>> 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.
Aha. I'd forgotten all about >>.
Thanks, everyone! I'm going with callFoo >> callBar >> return baz.
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