I wasn't at a computer with Haskell when I wrote the earlier message.  Here's how it seems to work.

File:
data MyType = MyType

instance Show MyType where
    show MyType = "a\nb"
   

Load the above file. Then:

> MyType        -- This does what I want it to do after all.
a
b

> show MyType 
"a\nb"

> putStrLn (show MyType)
a
b

> print MyType 
a
b



-- Russ Abbott
_____________________________________________
  Professor, Computer Science
  California State University, Los Angeles

  Google voice: 424-235-5752 (424-cell-rja)
  blog: http://russabbott.blogspot.com/
  vita:  http://sites.google.com/site/russabbott/
_____________________________________________



On Tue, Nov 9, 2010 at 9:40 AM, Russ Abbott <russ.abbott@gmail.com> wrote:
Is there some way to include control characters in a Show string so that they take effect when the element is Shown?

For example, if I define a String "a\nb" and use putStrLn on it, the \n causes a return, but when I simply return the string from a function, the \n is shown as \n.  Is there a way to get the \n to execute when it's embedded in a returned value?

Thanks

-- Russ Abbott
_____________________________________________
  Professor, Computer Science
  California State University, Los Angeles

  Google voice: 424-235-5752 (424-cell-rja)
  blog: http://russabbott.blogspot.com/
  vita:  http://sites.google.com/site/russabbott/
_____________________________________________