Re: [Haskell-cafe] When using Cereal, what is the right way to write `get` for multi-constructor type?

On 26 April 2016 at 18:10, Magicloud Magiclouds wrote:

OK. So my understanding is there is no better (good-looking) code. Thank you all.

The only other thing I can think of is that if you use the DeriveGeneric extension to derive an instance of Generic for your class, then you can do just "instance Serialize STH" and the get and put instances will be defined for you. This doesn't work if you want custom/specified values for your constructors though.

William Yager 于2016年4月26日周二 下午4:03写道：

...

You may also want to use the Lambda-case extension. It will allow you to elide the declaration of i.

--Will Yager

On Tue, Apr 26, 2016 at 1:24 AM, Ivan Lazar Miljenovic wrote:

...

On 26 April 2016 at 15:39, Magicloud Magiclouds wrote:

...

Hi, Say I have code already like: data STH = A | B | C instance Serialize STH where put A = putWord8 1 put B = putWord8 66 put C = putWord8 111

Then what is the better way to do `get`? Is following the only one? get = do i <- getWord8 case i of 1 -> return A 66 -> return B 111 -> return C

I think that covers it, though having an explicit error message for any other value of `i` will probably be better than the default unmatched case one.

...

Thanks.

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com