[Haskell-beginners] How to construct complex string

[martin]

Am 08/06/2013 07:01 PM, schrieb Stephen Tetley:
> Hi Martin
> 
> If you are building syntax as a sequence of commands (or statements) a
> common idiom is to collect them with a Writer monad. 
> 
> Andy Gill's Dotgen on Hackage is a nice realization of this idiom. See
> the how example included in the package has acceptably nice syntax
> without obliging the implementation to use complex facilities such as
> Template Haskell.  

Thanks Stephen,

exactly the nudge I was looking for, except I could not find any
examples in the package. I had a brief look at the source code and it
did not instantly reveal itself.

Actually I already got stuck here:

data Dot a = Dot { unDot :: Int -> ([GraphElement],Int,a) }



Thanks Brent

for you detailed explanation.