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MathGroup Archive 1995

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Constructing expressions

  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg677] Constructing expressions
  • From: Scott Herod <sherod at newton.Colorado.EDU>
  • Date: Sat, 8 Apr 1995 13:03:24 -0600 (MDT)

Someone asked last night about a way to construct expressions
of a certain type.  I erased the message but then lay awake
thinking about an answer.  It is similar to some things that
I have had to work out in the past.  Anyway, here is a suggestion.
I'm not sure if I am reproducing exactly what was asked for
but hopefully it is close.

Here is some code:

Cat[a_,b_] := ToExpression[StringJoin[
    ToString[a], ToString[b]]];
ddd[x_[k_]] := Apply[x,Table[Cat[x,i],{i,k}]];
ddd[x_[k_,j__]] := Apply[x,
    Table[ddd[Cat[x,i][j]],{i,k}]];

Here is an example:

In[25]:=
ddd[t[2,2]]
Out[25]=
t[t1[t11, t12], t2[t21, t22]]

In[28]:=
ddd[t[2,2,3]]
Out[28]=
t[t1[t11[t111, t112, t113], t12[t121, t122, t123]], 
  t2[t21[t211, t212, t213], t22[t221, t222, t223]]]


Scott Herod
Applied Mathematics
University of Colorado, Boulder
sherod at newton.colorado.edu


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