[Haskell-begin] data declarations

[Jeff Zaroyko]

Brandon S. Allbery KF8NH <allbery <at> ece.cmu.edu> writes:

> 
> 
> On 2008 Jul 22, at 23:01, Roger Myers wrote:
> 
> > Not sure if I'm on the right track here, so as a beginner I thought  
> > I'd ask on
> > this list.
> >
> > I want to declare a type 'All' that consists of the of the types  
> > 'Tinteger,
> > Tbool, Tstring, Tarray' but I would also like to make a relationship  
> > that
> > Tinteger and Tbool are also the type 'Simple' and that 'Tstring' and  
> > 'Tarray'
> > are 'Composite' and that Mixed is then either Simpletype or Composite.
> >
> > So I can then write a function that takes a type of All and produces  
> > a list of
> > Mixed.
> 
> Any particular reason that All can't be represented by Mixed?  That  
> would be my first cut at it (assuming I didn't need advanced type  
> hackery for some reason).
> 

Hmm... ah, bad thinking on my part.  I think this serves me a lot better:


data Simple = Tinteger Int
            | Tbool Bool
data Composite = Tstring String
               | Tarray [All]

data All = Simple | Composite

k :: All -> [All]
k a = case a of
        Simple -> [a]
        Composite -> [a]


Thanks :)