5.1.31 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 mapping 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

See imap; map; qring; ring.