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Re: Why is Mathematica assuming k==l and how do I make it

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92724] Re: Why is Mathematica assuming k==l and how do I make it
  • From: "sjoerd.c.devries at gmail.com" <sjoerd.c.devries at gmail.com>
  • Date: Sat, 11 Oct 2008 06:46:09 -0400 (EDT)
  • References: <gci2il$td$1@smc.vnet.net> <gcn4a5$75e$1@smc.vnet.net>

First of all you should put your question as a new posting and not
hijack a thread that has nothing to do with it.

Secondly, you really should try to read some basic documentation on
Mathematica. Just looking at someone's code and starting a newsgroup
discussion for every element your unfamiliar with is rather
inefficient, to say the least.

Anyway, to answer your question: [[ .. ]] are used to indicate array
indices. Single brackets [ .. ] are used for function arguments.

Sjoerd

On Oct 10, 10:38 am, mariam <mariamsaleh.k... at gmail.com> wrote:
> On Oct 8, 12:38 pm, Bob Hanlon <hanl... at cox.net> wrote:
>
>
>
> > Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi},
> >  Assumptions -> {l == k, Element[{l, k}, Integers]}]
>
> > Pi
>
> > Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi},
> >  Assumptions -> {l != k, Element[{l, k}, Integers]}]
>
> > 0
>
> > Assuming[{l == k, Element[{k, l}, Integers]},
> >  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> > Pi
>
> > Assuming[{l != k, Element[{k, l}, Integers]},
> >  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> > 0
>
> > Bob Hanlon
>
> > ---- Aaron Fude <aaronf... at gmail.com> wrote:
>
> > =============
> > As in
>
> > Assuming[Element[{k, l}, Integers] ,
> >  Integrate[Cos[k alpha] Cos[l alpha], {alpha, -Pi, Pi}]]
>
> > I get 0 whereas the answer is Pi if k=l;
>
> > Thanks!
>
> > Aaron
>
> > --
>
> > Bob Hanlon
>
> hi all,
> i found your group via web-search.
> i am new to mathematica and learning about some codes needed in my
> projects.
> i want to know that:
> 1)
>
> Do[{
>         amplist[i1]= Read[StringJoin[jproc,"/",QCD[i1],"diagram=
s.amp"]],
>         ileng[i1] = Length[amplist[i1]],
>
>         Do[{
>         Print["Processing amp[",i1,",",i2,"]"],
>         If[i1===2,{amp[i1,i2] = amplist[i1][[i2]][[3]]}, =
{amp[i1,i2] =
> amplist[i1][[i2]][[2]]
>                                     =
                                     =
                 }],
> ---------------------------------- and so on.
>  What does amp[i1,i2] = amplist[i1] [[i2]] [[3]] mean? I mean any
> f[i.j]=g[i] [[j]] [[k]]
> I am confused about the double-brackets used  [[----]].
>
> 2) in another expression,
> itwo = StringPosition[jproc,"2"][[1,1]]
>
> what for [[ x, y]] is used?
>
> I'll be very grateful for your help.



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