Derka, nice trick, using logcontract in two different regimes.
A few additional minor comments on the code:
* There is no reason to put _s and _z in the block variables. They are
local to their lambdas already.
* If you *do* want to define exp_log_to_power locally, you need to add
local(exp_log_to_power) after the block variable declaration.
* But I agree with Barton that you might as well make it global. If it is
strictly a helper function, useless for anyone else, you can call it
something like expcontract_exp_log_to_power.
* It's good practice to always quote symbolic constants: logexpand: 'super
* You probably want to restrict to something more than just not-atom in the
scanmap lambda; logcontract(log(...)) won't do anything useful for function
calls, subscripted variables, etc. It won't do any damage either, but by
that reasoning, you can just remove the 'if atom' clause. On the other
hand, you probably want to protect against constructing log(0) in e.g.
expcontract of [0] or atan2(x,0).
-s
On Mon, May 20, 2013 at 10:12 AM, Barton Willis <willisb at unk.edu> wrote:
> You might consider:
>
> (1) placing the assignment logexpand: super inside a block--your code
> globally alters logexpand
>
> (2) moving the definition of exp_log_to_power to outside the body of
> expcontract--the definition of
> exp_log_to_power is global--it gets redefined everytime expcontract
> is called.
>
> And by the way: if you like the leading underscores on variable, that's
> OK. But for this code, there is
> no need to wartify the variable names. Actually, I think that leading
> underscores makes code harder
> to read, and it makes me more likely to make errors (one place _z another
> z).
>
> --Barton
>
> ________________________________________
>
> I have a idea (combined previous)
>
> expcontract(_expr):=block([_z],
> exp_log_to_power(_e):= block([_s, logconcoeffp: lambda([_s],true)],
> logcontract(_e)),
> logexpand: super,
> scanmap(lambda([_z],if atom(_z) then _z else (
> exp_log_to_power(exp(logcontract(log(_z))))
> )),_expr)
> )$
>
> expr: x^a*y^a$
> expcontract(expr);
> -> (x*y)^a
>
> expr: (a^d*b^d+c^a*a^a)/(d^b*e^b+a^b*c^b)$
> expcontract(expr);
> -> ((a*b)^d+(a*c)^a)/((d*e)^b+(a*c)^b)
>
> Derka
>
>
>
>
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