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5.1.52 imap

Syntax:
imap ( ring_name, name )
Type:
number, poly, vector, ideal, module, matrix or list (the same type as the second argument)
Purpose:
identity map on common subrings. imap is the map between rings and qrings with compatible ground fields which is the identity on variables and parameters of the same name and 0 otherwise. (See map for a description of possible mappings between different ground fields). Useful for mapping from a homogenized ring to the original ring or for mappings from/to rings with/without parameters. Compared with fetch, imap uses the names of variables and parameters. Unlike map and fetch imap can map parameters to variables.
Example:
 
  ring r=0,(x,y,z,a,b,c),dp;
  ideal i=xy2z3a4b5+1,homog(xy2z3a4b5+1,c); i;
==> i[1]=xy2z3a4b5+1
==> i[2]=xy2z3a4b5+c15
  ring r1=0,(a,b,x,y,z),lp;
  ideal j=imap(r,i); j;
==> j[1]=a4b5xy2z3+1
==> j[2]=a4b5xy2z3
  ring r2=(0,a,b),(x,y,z),ls;
  ideal j=imap(r,i); j;
==> j[1]=1+(a4b5)*xy2z3
==> j[2]=(a4b5)*xy2z3
See fetch; homog; map; qring; ring.

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