MathGroup Archive 1996

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Generating inverse functions

  • To: mathgroup at
  • Subject: [mg3493] Generating inverse functions
  • From: "T. Daniel Crawford" <crawdad at>
  • Date: Mon, 18 Mar 1996 00:56:42 -0500
  • Organization: Center for Computational Quantum Chemistry
  • Sender: owner-wri-mathgroup at

I was wondering if anyone out there has any advice for me on the 
construction of the inverse of a function supplied by the user.
These functions have only symbolic arguments.  For example,

The user provides us with:

func[i] = 1; func[j] = 2; func[k] = 3; func[l] = 4;

We would like to automatically construct the inverse function:

funcInverse[1] = i;
funcInverse[2] = j;
funcInverse[3] = k;
funcInverse[4] = l;

Perhaps this question has an obvious answer, but I don't see it.  Of
course, if the functions were numerical and we knew their domain and
range, we could simply generate the inverse with a loop.  In this case,
though, we don't know what domain the original function might have.  Is
there a way to use Mathematica's stored values for the original function
to build the inverse?

Thanks in advance for any help you can provide!
T. Daniel Crawford			Center for Computational Quantum
crawdad at			    Chemistry


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