Re: [Haskell-beginners] How to add a "method" to a record

Bear in mind you can just create functions at the top level that operate on your data structure. You only need the function to be a member of the record if the function itself changes, which is relatively rare. Say you need a Foo and a Bar, and they both have labels, implemented in different ways, then you can use a typeclass to achieve your goals. On Wednesday, September 10, 2014, David McBride wrote:

Is this what you are looking for?

data Foo pl = Foo { label :: pl -> String, payload :: pl }

On Wed, Sep 10, 2014 at 2:06 PM, martin javascript:_e(%7B%7D,'cvml','martin.drautzburg@web.de');> wrote:

...

Hello all

if I have a record like

data Foo pl = Foo { label :: String, payload :: pl }

how can I create a similar type where I can populate label so it is not a plain string, but a function which operates on payload? Something like

label (Foo pl) = show pl

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