Il Fri, Sep 01, 2006 at 10:43:14AM +0400, Bulat Ziganshin ebbe a scrivere:
The tutorial will have this outline: first we build a monad adding output, exception, and state. Then we use monad transformer to take out state and output and add debug, doing lifting, put(ing) and get(ing) by hand, to understand the central role of type matching/construction.
imho, your tutorial makes the error that is a very typical: when you write your tutorial you already know what are monads and what the program you will construct at the end. but your reader don't know all these!
Neither did I, actually.
for such fresh reader this looks as you made some strange steps, write some ugly code and he don't have chances to understand that this ugly code is written just to show that this can be simplified using monads. i've tried to read it imaging myself as fresh reader and was stopped at some middle because code was too complicated to understand and it was completely imobvious (for fresh reader) that we just wrote "innards" of monad and then will reduce all this ugly code just to ">>=" calls
I do not entirely understand your point. I wrote just the first part of the tutorial, till the "Errare Monadicum Est" chapter. From then on, before writing the tutorial, I needed to understand what I was headed to and so I wrote the code. Now the task is to explain each step of that code. Indeed I'm a fresh reader that did not find anything that she could find useful to understand monads, and wrote her own. That is to say, this is the way I came to understand monads. I do not pretend to teach what monads are, but I hope that, by following the same path I followed, someone else can get to the point where I am now. Where now I am is just another kind of problem. Probably nowhere. That's it. Anyway, thanks a lot for your suggestions. I'll try to understand them and put them in practice. As far as I can. Best regards, Andrea