[Haskell-cafe] Abuse of the monad [was: monadic logo]

Andrew Wagner wagner.andrew at gmail.com
Thu Mar 12 10:46:51 EDT 2009

Hmm, perhaps what we need is another monad tutorial that.....err...never
mind. Actually, I'd like to see more written about Applicatives. I think
they just finally clicked with me when reading the Typeclassopedia, and
seeing the intended way to use them. Before it was always like "ok...so, if
I've got a function already in my functor, I could use this, but...why would
I have that?"

On Thu, Mar 12, 2009 at 10:28 AM, Thomas Davie <tom.davie at gmail.com> wrote:

> On 12 Mar 2009, at 15:16, Andrew Wagner wrote:
>  Can you expand on this a bit? I'm curious why you think this.
> For two reasons:
> Firstly, I often find that people use the Monadic interface when one of the
> less powerful ones is both powerful enough and more convenient, parsec is a
> wonderful example of this.  When the applicative instance is used instead of
> the monadic one, programs rapidly become more readable, because they stop
> describing the order in which things should be parsed, and start describing
> the grammar of the language being parsed instead.
> Secondly, It seems relatively common now for beginners to be told about the
> IO monad, and start writing imperative code in it, and thinking that this is
> what Haskell programming is.  I have no problem with people writing
> imperative code in Haskell, it's an excellent imperative language.  However,
> beginners seeing this, and picking it up is usually counter productive –
> they never learn how to write things in a functional way, and miss out on
> most of the benefits of doing so.
> Hope that clarifies what I meant :)
> Bob
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