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Topic: List Replace Problems
Replies: 8   Last Post: Aug 30, 2005 4:44 AM

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wes

Posts: 24
Registered: 12/13/04
List Replace Problems
Posted: Aug 23, 2005 5:01 AM
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I want to perform some element by element operations on a class of
lists. For a given list The operation in a much simplified form can be
characterized by

a = {1, 3, 5, 7, 9};
Do[a[[i]] /= i, {i, 1, 5}];
a

Out[38]=
{1, 3/2, 5/3, 7/4, 9/5}

Now, however, if I try to define a function to do this for a general
list, namely,

dlst[u_List] =
Do[u[[i]] /= i, {i, 1, 5}];
a = {1, 3, 5, 7, 9};
dlst[a];
a

Set::setps:
({1, 2, 3, 4, 5}) in assignment of part is not a symbol. ! More ...

Out[39]=
{1, 3, 5, 7, 9}

I get the above error. It says I'm trying to assign one number to
another number. Why does Mathematica perform in the first case but
refuse to in the second.

I tried

b = Do[ReplacePart[a, a[[i]]/i, i], {i, 1, 5}]

but it doesn't even bother to return an error message.


How, can I get the desired function?

Thanks,

Wesh




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