Re: how to make Sum[n,{n,1,5}] to print 1+2+3+4+5? HoldForm?
- To: mathgroup at smc.vnet.net
- Subject: [mg79425] Re: how to make Sum[n,{n,1,5}] to print 1+2+3+4+5? HoldForm?
- From: dimitris <dimmechan at yahoo.com>
- Date: Thu, 26 Jul 2007 05:37:59 -0400 (EDT)
- References: <f86qdq$o7p$1@smc.vnet.net>
On 25 , 09:26, Nasser Abbasi <n... at 12000.org> wrote:
> hi, I am using version 6
>
> what is the trick to make Sum[] just print the terms first, before
> adding them? Say I want to do
>
> r= Sum[n,{n,1,5}]
>
> But I want to see 1+2+3+4+5, i.e. the terms printed out before they
> are actually added.
>
> then later I can do Evaluate[r] or N[r] something like this to get it
> to actually do the sum.
>
> I tried the different Hold commands, but non seems to do it.
>
> thanks,
> Nasser
The simplest thing is
In[4]:=
Sum[(HoldForm[#1] & )[i], {i, 1, 5}]
ReleaseHold[%]
Out[4]=
1+2+3+4+5
Out[5]=
15
But what is more elegant is (at least for me)
to write the sum as 1+2+3+4+5+...
and do all the things you can encounter
in any textbook like summation/multiplication
etc with another similar expression.
I think that David Park is working with this issue.
Regards
Dimitris