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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
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See
fetch;
homog;
map;
qring;
ring.
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