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 Intersection

intersect lists, ideals, or modules
 Syntax
 ``` Intersection(E_1:LIST,....,E_n:LIST):LIST Intersection(E_1:IDEAL,...,E_n:IDEAL):IDEAL Intersection(E_1:MODULE,....,E_n:MODULE):MODULE ```

 Description
The function Intersection returns the intersection of E_1,...,E_n. In the case where the E_i's are lists, it returns the elements common to all of the lists.

The coefficient ring must be a field.

NOTE: In order to compute the intersection of inhomogeneous ideals, it may be faster to use the function HIntersection. To compute the intersection of ideals corresponding to zero-dimensional schemes, see the commands GBM and HGBM .

 Example
 ``` Use R ::= QQ[x,y,z]; Points := [[0,0], [1,0], [0,1], [1,1]]; -- a list of points in the plane I := Ideal(x, y); -- the ideal for the first point Foreach P In Points Do I := Intersection(I, Ideal(x-P[1]z,y-P[2]z)); EndForeach; I; -- the ideal for (the projective closure of) Points Ideal(y^2 - yz, x^2 - xz) ------------------------------- Intersection(["a","b","c"], ["b","c","d"]); ["b", "c"] ------------------------------- ```