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Re: pick out an element from list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98082] Re: pick out an element from list
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Sun, 29 Mar 2009 02:48:46 -0500 (EST)
  • References: <gqkup8$458$1@smc.vnet.net>

On Mar 28, 3:39 am, bahadir <bahadirgurbu... at hotmail.com> wrote:
> i have a list with n element.i want to pick out an element from the list,=
 and to deduct the element from all the other residual elements. This proce=
ss is the first step. i must apply all elements of the list, invariably. Na=
mely, in conclusion, i will obtain n list with n-1 elements. now, i will tr=
y to explain as numerically. let element number of the list be 2500. and i =
am picking out the first element of the list. and i'm deducting the first e=
lement from the residual elements of the list. and now, i have a list with =
2499 elements.after that, i'm passing the second element, and i'm applying =
the same processes. =C4=B1 can't do this, can anyone help me???

The process simplifies. If the intial list is {a, b, c, d} then
the first step gives {a, b-a, c-a, d-a}. The second step gives
{a, b-a, (c-a)-(b-a), (d-a)-(b-a)} = {a, b-a, c-b, d-b}. Finally,
the third step gives {a, b-a, c-b, (d-b)-(c-b)} = {a, b-a, c-b, d-c}.

In[1]:= (#-Join[{0},Most@#]&) @ {a,b,c,d,e,f}

Out[1]= {a, -a+b, -b+c, -c+d, -d+e, -e+f}


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