Re: A simple swap function
- To: mathgroup at smc.vnet.net
- Subject: [mg2233] Re: [mg2132] A simple swap function
- From: mmcclure at liberty.uc.wlu.edu (Mark McClure)
- Date: Wed, 18 Oct 1995 01:53:03 -0400
- Organization: Washington & Lee University
Richard Mercer (richard at seuss.math.wright.edu) 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?
: 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}];
Even if a and b have been assigned values, howabout
swap[{a_,b_}] := {b,a}
?
Mark
mmcclure at wlu.edu
http://wlu.edu/~mmcclure