Re: A simple swap function
- To: mathgroup at smc.vnet.net
- Subject: [mg2145] Re: A simple swap function
- From: rmarimon at leland.stanford.edu (Ricardo Marimon)
- Date: Wed, 4 Oct 1995 01:58:34 -0400
- Organization: Stanford University
In article <44qj8g$s22 at ralph.vnet.net>, valentin at wam.umd.edu (William F.
Campbell) wrote:
> I think I must be missing something straightforward. I want a function
> to swap the values of 2 lists. I defined ab={a,b}, and ba={b,a}, and
> swap[v1_,v2_]:=Module[{temp=v1},v1=v2;v2=temp;], and I get an Iteration
> limit exceeded error. When I look at ab, it looks like {Hold[a],Hold[b]}
> (or maybe {Hold[b],Hold[a], I don't remember), and ba looks opposite. When
> I tried to use the same function on numbers, it didn't work either. What's
> wrong with what I'm doing, and how can I do what I want to do?
If I remember correctly, the parameters in Mathematica are passed by value
only. Any attempt to change the value of a parameter will not work, since
you would be changing the value of the paramater and not the value of the
variable you passes to the function...
You could try writting
{v1, v2} = {v2, v1}
this will do the swap you intend and is very simple...
- Ricardo Marimon
rmarimon at leland.stanford.edu