[Haskell-cafe] Seeking advice on a style question

Conal Elliott conal at conal.net
Tue Dec 26 13:28:22 EST 2006


I like monadic reformulations when they remove repetitious patterns from
code, such as reading/updating a single threaded state.  I'm not yet seeing
such a pattern in your case.  As you mentioned:

The "shape" of the
> state isn't constant throughout the process. At any given step, new
> information may be added to the state, and old information may be thrown
> away, if there is no further need for it.
>

So I'm still doubtful that a monadic approach is going to simplify your
code.   Would you give a real example of some code you'd like to make more
manageable?  If you have real examples of State, Reader, and/or Writer
monads that strike you as similar to your example, please share that also.

Cheers, - Conal

On 12/26/06, Steve Schafer <steve at fenestra.com> wrote:
>
> On Mon, 25 Dec 2006 09:52:47 -0800, you wrote:
>
> >To my eye, your example code below looks less like an imperative
> >program than like an intermediate form that a compiler would generate
> >from an expression built up from nested function applications and a
> >few "let"s.
>
> That's very true, but the same could be said for many other examples
> of the use of the State monad (and Reader and Writer as well). They
> frequently don't do anything that couldn't be done purely
> functionally.
>
> Steve Schafer
> Fenestra Technologies Corp.
> http://www.fenestra.com/
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