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4.5.2 ideal expressions
An ideal expression is:
-
an identifier of type ideal
-
a function returning an ideal
-
a combination of ideal expressions by the arithmetic operations
+ or *
-
a power of an ideal expression (operator
^ or ** )
Note that the computation of the product i*i involves
all products of generators of i while i^2 involves
only the different ones, and is therefore faster.
-
a type cast to ideal
Example:
| ring r=0,(x,y,z),dp;
ideal m = maxideal(1);
m;
==> m[1]=x
==> m[2]=y
==> m[3]=z
poly f = x2;
poly g = y3;
ideal i = x*y*z , f-g, g*(x-y) + f^4 ,0, 2x-z2y;
ideal M = i + maxideal(10);
timer =0;
i = M*M;
timer;
==> 0
ncols(i);
==> 505
timer =0;
i = M^2;
ncols(i);
==> 505
timer;
==> 0
i[ncols(i)];
==> x20
vector v = [x,y-z,x2,y-x,x2yz2-y];
ideal j = ideal(v);
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