Re: Newbie question: what's this dot?

"Kjetil S. Matheussen" <k.s.matheussen@xxxxxxxxxx> writes:

On Thu, 31 May 2007, Joel J. Adamson wrote:

when I divide using

(/ 1 2)

or

(quotient 1 2)

I get 1/2.

When I divide using

(/ 1 2.)

I get 0.5

As I want to use this to calculate Taylor series and other such
sequences, I really need the decimal representation.

Why?

Because the point of the program is to print out the partial sums of a
series, and also find the limit of a series, or tell me that it's
divergent. This is just for learning.

How do I coerce
this (do I need to coerce it or is this much simpler)?

For example, if I

(define series
(lambda (x)
(/ 1 x)))

and then do

(map series '(1 2 3 4 5))

I get a list of ones as a result. That's not right ;)

Really?

Really.

Then your scheme is broken. This is what you are supposed to get:
(1 1/2 1/3 1/4 1/5)

Hmmm, it's definitely treating them as integers and giving me the
integer ceiling. I'm pretty sure it's doing what it's supposed to do,
and I'm not doing what I'm supposed to do. I hope you consider that a
productive attitude.

I'm not sure, but I have a feeling that you don't know the concept of
rationals in lisp?

Bingo. I will read about it.

(btw, I know the concept of rational in mathematics, and so perhaps
thinking of it as a subset of real numbers is what's tripping me up;
these things seem to have a different meaning; i.e., to scheme, a
rational and an integer are different, to me they are the same in the
sense that an alligator is a crocodile, i.e., subsets).

Thanks for your help,

Joel

--
Joel J. Adamson
Biostatistician
Pediatric Psychopharmacology Research Unit
Massachusetts General Hospital
Boston, MA 02114
(617) 643-1432
(303) 880-3109
.

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