Re: [Chicken-users] [ANN] Monad Egg

[Jörg F . Wittenberger]

On Apr 13 2012, Daniel Leslie wrote:

> (define-monad
> >  <complex-id>
> >  (lambda (r i) (values r i))
> >  (lambda (f r i) (f r i)))
>
> Why not:
>
> (define-monad <cid> (lambda (a) (values (car a) (cdr a)))
>    (lambda (a f) (f (car a) (cdr a))))
>
> That's how the <logger> monad example goes about things. The parameter list
> itself is just compacted into a pair, and passed through the unit and bind
> functions.
>
> I suppose I could extend it to support a full parameter list... It's
> certainly worth considering.

I'm pretty confused now.

A) About the parameter order.
B) the approach to multiple values.

Let's start with (B) for logic even though unimportant

> (define-monad <cid> (lambda (a) (values (car a) (cdr a)))
>    (lambda (a f) (f (car a) (cdr a))))

Confused I am because where the identity returns one
value it return now two.  Access however is as if it
had returned a list.

As for (A): The API-point of mine derives from the consideration,
what changes would be needed to support a full parameter list.
This lead me to see the "f" parameter as naturally in the first
position.  Not

> (define-monad <id> (lambda (a) a)
>    (lambda (a f) (f a)))

but

> (define-monad <id> (lambda (a) a)
>    (lambda (f a) (f a)))

I would prefer.  I feel it looks more natural when extended to

> (define-monad <cid> (lambda (a b) (values a b))
>    (lambda (f a b) (f a b)))

because the "f" is always in "operator position".

/Jerry
......