On 06/03/14 03:53, David Fox wrote:
Show is supposed to convert its argument into a haskell expression which, when evaluated, returns the same value that was initially passed to show. So by this definition, "\252" is just as correct as "ü".
There are some Show instances out in the world that do not follow this rule, but they are bad. I'm looking at you, Network.URI!
What about instances where we can't have a reasonable Show that fulfills your requirement? Say, any structure which encapsulates a function. While I agree that ideally Show (or some other typeclass) would be used so that ‘read’ also works, it's not always possible. If people are expected to follow the implicit Show rules then perhaps base functions such as ‘print :: Show a => a -> IO ()’ shouldn't be using Show to begin with! It's inconvenient to not make Show instances/make the instances be readable if all the functions that actually let us have a look at the structures use ‘Show’. ‘print’ is great and no one is going to abandon in because one of the 30 fields in their structure happens to be a function. -- Mateusz K.