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Xah Lee
Posts:
171
Registered:
12/4/04


Re: manipulating expressions
Posted:
Jun 28, 1996 9:43 AM


Xah Lee wrote: > I have an expression, for example > (16 a^4  8 a^2 m^2 + m^4  8 a^2 n^2 + 2 m^2 n^2 + n^4  > 8 a^2 p^2  2 m^2 p^2  2 n^2 p^2 + p^4  8 a^2 q^2  > 2 m^2 q^2  2 n^2 q^2 + 2 p^2 q^2 + q^4 ) > that I want to write in a concise form, namely, as a sum of a few > products. There are many possibilities and it's tedious to form each. > How would you write a Mathematica program that would take such an > expression and spits out a few choicy forms for the user?
I posted the above problem and only one person replied with a code. Here's killough@wagner.convex.com (Lee D. Killough)'s solution:
simple[x_,v_]:=Sum[v^i Factor[Coefficient[#,v,i]], {i,0,Exponent[#,v]}]&[Expand[x]]
simple[x_] := First @ Sort[simple[x,#]& /@ Variables[x], Less @@ ( StringLength @ ToString @ # & /@ {##} )& ]
Here's a quick documentation
simple::usage = "simple[expr] returns the concise expression as a sum of factors. simple[expr,x] returns the expression as a sum of factors of x."
Xah xah@best.com; 74631.731@compuserve.com http://www.best.com/~xah/SpecialPlaneCurves_dir/specialPlaneCurves.html Mountain View, CA, USA URL of the day: All Philosophers love you in N.Y. http://nifty.bookstore.uidaho.edu/Philosophy/Default.htm



