[Haskell-cafe] Transformation sequence

[Brandon S. Allbery KF8NH]

On Oct 20, 2007, at 15:05 , Andrew Coppin wrote:

> I can quite happily construct a program which, given the first  
> line, yields the last line. But getting it to print all the  
> intermediate steps is harder. And, like I said, when something is  
> "hard" in Haskell, it usually means you're doing it the wrong  
> way... ;-)

This is the Writer monad.

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH