factor does not work as expected

On 02/01/2011 12:25 AM, Stavros Macrakis wrote:
> radcan(h) will combine the powers.
>
> To extract all x such that x^base appears in expr, how about:
>
> powers_of(expr,base):=block([inflag:true],
>                   if mapatom(expr) then [] elseif part(expr,0) = "^" and
> part(expr,1) = base then [part(expr,2)]
>                       else
> apply('append,maplist(lambda([ex],powers_of(ex,base)),expr)))

Very nice, thank you for the quick response
Andre

> On Mon, Jan 31, 2011 at 17:55, andre maute<andre.maute at gmx.de>  wrote:
>
>> suppose one has
>> ----factor.max---------------------
>>
>> display2d : false;
>>
>> declare(a_1,integer);
>> declare(a_2,integer);
>> declare(a_3,integer);
>>
>> assume(1-xbar_1>  0);
>> assume(1-xbar_2>  0);
>>
>> assume(a_1>= 0);
>> assume(a_2>= 0);
>> assume(a_3>= 0);
>>
>> h :
>> 2^(a_2-a_1)*4^(a_3-a_2)*(1-xbar_2)^(a_3+a_2)*(1-xbar_1)^(a_3+a_2+a_1)/8^a_3;
>>
>> factor(ratsimp(h));
>> ----factor.max---------------------------
>>
>> maxima -b factor.max
>>
>> gives
>> -------output---------------------------
>> Maxima 5.19.2 http://maxima.sourceforge.net
>> Using Lisp SBCL 1.0.40-1.fc14
>> Distributed under the GNU Public License. See the file COPYING.
>> Dedicated to the memory of William Schelter.
>> The function bug_report() provides bug reporting information.
>> (%i1)                          batch(factor.max)
>>
>> batching /home/user/factor.max
>> (%i2)                          display2d : false
>> (%o2) false
>> (%i3) declare(a_1,integer)
>> (%o3) done
>> (%i4) declare(a_2,integer)
>> (%o4) done
>> (%i5) declare(a_3,integer)
>> (%o5) done
>> (%i6) assume(1-xbar_1>  0)
>> (%o6) [xbar_1<  1]
>> (%i7) assume(1-xbar_2>  0)
>> (%o7) [xbar_2<  1]
>> (%i8) assume(a_1>= 0)
>> (%o8) [a_1>= 0]
>> (%i9) assume(a_2>= 0)
>> (%o9) [a_2>= 0]
>> (%i10) assume(a_3>= 0)
>> (%o10) [a_3>= 0]
>> (%i11)
>> h:2^(a_2-a_1)*4^(a_3-a_2)*(1-xbar_2)^(a_2+a_3)*(1-xbar_1)^(a_1+a_2+a_3)
>>          /8^a_3
>> (%o11)
>> 2^(a_2-a_1)*4^(a_3-a_2)*(1-xbar_1)^(a_3+a_2+a_1)*(1-xbar_2)^(a_3+a_2)
>>         /8^a_3
>> (%i12) factor(ratsimp(h))
>> (%o12)
>> 2^(a_2-a_1)*4^(a_3-a_2)*(1-xbar_1)^(a_3+a_2+a_1)*(1-xbar_2)^(a_3+a_2)
>>         /8^a_3
>> (%o12) "/home/puck/factor.max"
>> -------output---------------------------
>>
>> 1. Question:
>> Is it possible to force maxima to combine the integer powers?
>>
>> 2. Question:
>> How can I extract the exponents of (1-xbar_1) respectively (1-xbar_2)?
>>
>> Thanks
>> Andre
>>
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