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D.4.1.2 absFactorizeBCG
Procedure from library absfact.lib (see absfact_lib).
- Usage:
- absFactorizeBCG(p [,s]); p poly, s string
- Assume:
- coefficient field is the field of rational numbers or a
transcendental extension thereof
- Return:
- ring
R which is obtained from the current basering
by adding a new parameter (if a string s is given as a
second input, the new parameter gets this string as name). The ring
R comes with a list absolute_factors with the
following entries:
| absolute_factors[1]: ideal (the absolute factors)
absolute_factors[2]: intvec (the multiplicities)
absolute_factors[3]: ideal (the minimal polynomials)
absolute_factors[4]: int (total number of nontriv. absolute factors)
| The entry absolute_factors[1][1] is a constant, the
entry absolute_factors[3][1] is the parameter added to the
current ring.
Each of the remaining entries absolute_factors[1][j] stands for
a class of conjugated absolute factors. The corresponding entry
absolute_factors[3][j] is the minimal polynomial of the
field extension over which the factor is minimally defined (its degree
is the number of conjugates in the class). If the entry
absolute_factors[3][j] coincides with absolute_factors[3][1] ,
no field extension was necessary for the j th (class of)
absolute factor(s).
- Note:
- All factors are presented denominator- and content-free. The constant
factor (first entry) is chosen such that the product of all (!) the
(denominator- and content-free) absolute factors of
p equals
p / absolute_factors[1][1] .
Example:
| LIB "absfact.lib";
ring R = (0), (x,y), lp;
poly p = (-7*x^2 + 2*x*y^2 + 6*x + y^4 + 14*y^2 + 47)*(5x2+y2)^3*(x-y)^4;
def S = absFactorizeBCG(p) ;
==>
==> // 'absFactorizeBCG' created a ring, in which a list absolute_factors (th\
e
==> // absolute factors) is stored.
==> // To access the list of absolute factors, type (if the name S was assign\
ed
==> // to the return value):
==> // setring(S); absolute_factors;
==>
setring(S);
absolute_factors;
==> [1]:
==> _[1]=1
==> _[2]=-x+y
==> _[3]=(-a)*x+y
==> _[4]=(2a-13)*x+y2+(a)
==> [2]:
==> 1,4,3,1
==> [3]:
==> _[1]=(a)
==> _[2]=(a)
==> _[3]=(a2+5)
==> _[4]=(a2-14a+47)
==> [4]:
==> 12
| See also:
absFactorize;
absPrimdecGTZ;
factorize.
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