Show is not meant to necessarily be human readable. It is meant to be the exact opposite of Read. You show it, then you read it back in and it is unambiguous. Having different ways to show it kind of defeats the purpose of show.

Most people just make a custom function that takes a macaddress and some other parameter to determine which format you want it to be output as and then just use that.

On Wed, Aug 7, 2013 at 1:04 PM, Chris Schneider <chris@christopher-schneider.com> wrote:

Hi, I'm writing a module that contains a data type for a MacAddress.

Given that, I can do things like validate and format.

But there are several ways you can display a MacAddress:

'aabbccddeeff' or '00:11:22:33:AA:BB' or 'aa:bb:cc:00:11:22'.

Different external systems want the mac addresses in different formats, and I'd like to centralize that logic.

** So the design question:

I can't just use a `show` function directly to do this, since there are options I need to pass.

I could use separate functions that return a string.

I could use newtype to wrap each display style of mac address in a type that has a specific `show` instance that spits out the right format. So a `Pretty` and `Lower` and similar types.

---

Is there a best-practice here? Am I totally missing a better way to model this idea?

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