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5.1.34 fetch
Syntax:
fetch ( ring_name, name )
Type:
- number, poly, vector, ideal, module, matrix or list
(the same type as the second argument)
Purpose:
- maps objects between rings.
fetch is the identity map between rings and qrings,
the i-th variable of the source ring is mapped to the i-th
variable of the basering. The coefficient fields must be compatible.
(See map for a description of possible mappings between
different ground fields).
fetch offers a convenient way to change
variable names or orderings, or to map objects from a ring to a quotient
ring of that ring or vice versa.
Note:
- Compared with
imap , fetch uses the position of the ring
variables, not their names.
Example:
| ring r=0,(x,y,z),dp;
ideal i=maxideal(2);
ideal j=std(i);
poly f=x+y2+z3;
vector v=[f,1];
qring q=j;
poly f=fetch(r,f);
f;
==> z3+y2+x
vector v=fetch(r,v);
v;
==> z3*gen(1)+y2*gen(1)+x*gen(1)+gen(2)
ideal i=fetch(r,i);
i;
==> i[1]=z2
==> i[2]=yz
==> i[3]=y2
==> i[4]=xz
==> i[5]=xy
==> i[6]=x2
ring rr=0,(a,b,c),lp;
poly f=fetch(q,f);
f;
==> a+b2+c3
vector v=fetch(r,v);
v;
==> a*gen(1)+b2*gen(1)+c3*gen(1)+gen(2)
ideal k=fetch(q,i);
k;
==> k[1]=c2
==> k[2]=bc
==> k[3]=b2
==> k[4]=ac
==> k[5]=ab
==> k[6]=a2
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See
imap;
map;
qring;
ring.
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