product ? *** and sum ? ***

07292014, 05:22 AM
(This post was last modified: 07312014 02:00 AM by Helge Gabert.)
Post: #1




product ? *** and sum ? ***
I just ran into this  
in Home: product(N,N,1,3,.5) runs fine But product(N,N,.5,3,.5) does not run and returns the arguments as multiplicands. in CAS: product(n,n,1,3,1/2) runs fine But again, product(n,n,1/2,3,1/2) returns 3/4*n^2. It appears that the minimum value is not to be less than one, which is strange. 

07292014, 11:19 AM
Post: #2




RE: product ?
According to the manual the arguments (a, b, and p) should be integers:
Code: product(ExprLst,[VarLst],[Intg(a)],[Intg(b)],[Intg(p)]) It turns out that the step size (p) could be nonintegral, but a and b must be integers. Otherwise you'll get those "list products" (e.g. multiplication of all 5 arguments). 

07292014, 03:35 PM
Post: #3




RE: product ?
Apparently so. Maybe this requirement can be relaxed in the future, so that the product command becomes more useful.


07292014, 04:58 PM
Post: #4




RE: product ?
Of course one could rewrite product(N,N,0.5,3,0.5) as product(N/2,N,1,6,1) and would get the correct answer (45/4).


07292014, 07:09 PM
Post: #5




RE: product ?
Yes, that would be an easy one to transform.
Others won't be, however. 

07302014, 03:43 PM
Post: #6




RE: product ?
If arg3 and arg4 are not integers, product behaves like if you input a list of values, it makes the product of the elements of the list. I'm going to modify product:
 if the argument is a list (with [] or {} delimiters) or does not have 5 args, no change  if the argument is a sequence with 5 arguments, do what you want 

07312014, 12:39 AM
(This post was last modified: 07312014 01:58 AM by Helge Gabert.)
Post: #7




RE: product ? and sum ?
Thank you. That would be great, and maybe we'll see that in the Prime, too!
[Edit: Actually, sum behaves similarly. Would it be possible to modify product and sum in the same way?] 

07312014, 07:42 AM
Post: #8




RE: product ? *** and sum ? ***
There is nothing to do for that, since it's in the common code product and sum share.


07312014, 03:24 PM
Post: #9




RE: product ? *** and sum ? ***
OK, thanks for replying!


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