[Haskell-cafe] F# active patterns versus GHC's view

[Henning Thielemann]

On Fri, 16 Jan 2009, John Van Enk wrote:

> 2009/1/16 Peter Verswyvelen <bugfact at gmail.com>
>
>> [...]
>>
>> After a while you decide that you need to change the Bla data type, maybe
>> give Dog more fields, maybe completely redesign it, maybe not exposing it,
>> but you want to keep existing code backwards compatible. With F# you can
>> write Active Patterns for the old Dog and Cat constructors, so all existing
>> code remains compatible. At least that is the way I understand it, but I
>> have not actually worked yet with Active Patterns, will do so soon :)
>>
> You get something similar with the record syntax (though, probably still not
> quite as powerful as the active patterns):

... or use data-accessor package.