[Haskell-cafe] do vs. pattern matching

[Benjamin Edwards]

The do notation in this instance yields a nice advantage: if you want to
switch to a different monad to encapsulate failure you will meely need to
swap out the type signature and your function will need no further work.
On Aug 4, 2012 7:35 AM, "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:
>
>         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?
>
> Thanks,
> - Matthew
>
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