[Haskell-cafe] How efficient is read?

[Daniel Gorín]

On May 9, 2010, at 12:32 AM, Tom Hawkins wrote:
> I have a lot of structured data in a program written in a different
> language, which I would like to read in and analyze with Haskell.  And
> I'm free to format this data in any shape or form from the other
> language.
>
> Could I define a Haskell type for this data that derives the default
> Read, then simply print out Haskell code from the program and 'read'
> it in?  Would this be horribly inefficient?  It would save me some
> time of writing a parser.
>
> -Tom

If your types contain infix constructors, the derived Read instances  
may be almost unusable; see http://hackage.haskell.org/trac/ghc/ticket/1544