[Jprogramming] Re : Sigma notation

[Linda Alvord]

J finally gets it right !

 

   f=: 13 :'+/3^-i.y'

   f

[: +/ 3 ^ [: - i.

   f 10

1.49997

   f 11

1.49999

   f 12

1.5

   f 100

1.5

   f 1e5

1.5

   f 1e10

|domain error: f
|       f 1e10

   f 1e100

|domain error: f
|       f 1e100

   f 1e1000

|domain error: f
|       f _

 

 

This last result shouldn't be a domain error, should it? Eugene would have
liked it. 

 

 

     5!:4 <'f'

  -- [:          
  +- / --- +     
  │              
--+     -- 3     
  │     +- ^     
  L-----+   -- [:
        L---+- - 
            L- i.

   

Linda

 

-----Original Message-----
From: programming-bounces at forums.jsoftware.com
[mailto:programming-bounces at forums.jsoftware.com] On Behalf Of Roger Hui
Sent: Saturday, December 22, 2012 2:26 AM
To: Programming forum
Subject: Re: [Jprogramming] Re : Sigma notation

 

> Lambda considered harmful?  LOL

 

No, sigma considered harmful.  In conventional notation there's big sigma
for summation and big pi for product.  But how do you do max insert (>./)?

Min insert (<./)? And insert (^./)?  Etc.

 

Infinite series (products, etc.) best done by having infinite vectors.  See
*Remembering Eugene McDonnell*<
<http://www.jsoftware.com/papers/eem/eemapl2010.htm>
http://www.jsoftware.com/papers/eem/eemapl2010.htm>

 

    i. 4

0 1 2 3

 

    i. _

0 1 2 3 4 5 ...

 

    +/ 3 ^ - i. _

1.5

 

 

and *Bring Something Beautiful* < <http://archive.vector.org.uk/art10500390>
http://archive.vector.org.uk/art10500390> .

 

 

On Fri, Dec 21, 2012 at 11:08 PM, Alex Giannakopoulos <
<mailto:aegean at blueyonder.co.uk> aegean at blueyonder.co.uk> wrote:

 

> Very nice, Linda, thanks.

> That's just the example I needed.

> 

> I think I'm beginning to get the 'geist' of it now!

> 

> (Lambda considered harmful?  LOL)

> ----------------------------------------------------------------------

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http://www.jsoftware.com/forums.htm

> 

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