Re: A simple swap function
- Subject: [mg2151] Re: [mg2132] A simple swap function
- From: richard at seuss.math.wright.edu (Richard Mercer)
- Date: Tue, 10 Oct 1995 06:36:40 GMT
- Approved: usenet@wri.com
- Distribution: local
- Newsgroups: wri.mathgroup
- Organization: Wolfram Research, Inc.
- Sender: daemon at wri.com ( )
> 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?
All of this is unnecessary.
Assuming the variables a and b have been assigned values,
the assignment
{a,b} = {b,a}
works. Try it! I do NOT recommend this if a and b have not been
assigned values!
If you want to be ultracareful, you could use
swap[v1_Symbol,v2_Symbol]:=
If[ValueQ[v1] & ValueQ[v2], {v1,v2} = {v2,v1}];
Richard Mercer
Richard Mercer