[Haskell-cafe] Practical introduction to monads

[Greg Buchholz]

Paul Moore wrote:
> One thing I haven't found a really good discussion of, is practical
> examples of building monads. There's plenty of discussion of the IO
> monad, and the state monad, and a lot of good theory on monads, but
> although I've seen tantalising statements about how powerful the
> ability to define your own monads can be, but no really concrete
> examples - something along the lines of
> 
>   - here is problem X
>   - this might be our first cut at coding it
>   - we can abstract out this stuff, as a monad
>   - see how the code looks now, how much cleaner it is

    Maybe you could try going in the opposite direction, and convert
something like monadic parser combinators...

http://www.cs.nott.ac.uk/~gmh/bib.html#pearl

...it into their non-monadic form (explictly passing the parsed string
around).

> I've only skimmed - so pointers to areas in these documents I might
> have missed would be appreciated. On the other hand, pointers to
> papers I've missed altogether would also be gratefully received.

    I found the papers by Philip Wadler to be the most helpful...

    http://homepages.inf.ed.ac.uk/wadler/topics/monads.html

...especially _Monads for functional programming_ and 
_Imperative functional programming_.


Greg Buchholz