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D.4.5.9 select1
Procedure from library elim.lib (see elim_lib).
- Usage:
- select1(id,v); id = ideal/module/matrix, v = intvec
- Return:
- generators/columns of id containing at least one of the variables
with index an entry of v
- Note:
- use 'select' for selecting generators/columns containing all variables
with index an entry of v
Example:
| | LIB "elim.lib";
ring r=0,(x,y,t,s,z),(c,dp);
ideal i=x-y,y-z2,z-t3,s-x+y3;
ideal j=select1(i,1);j;
==> j[1]=x-y
==> j[2]=y3-x+s
module m=i*(gen(1)+gen(2)); m;
==> m[1]=[x-y,x-y]
==> m[2]=[-z2+y,-z2+y]
==> m[3]=[-t3+z,-t3+z]
==> m[4]=[y3-x+s,y3-x+s]
select1(m,1..2);
==> _[1]=[x-y,x-y]
==> _[2]=[-z2+y,-z2+y]
==> _[3]=[y3-x+s,y3-x+s]
select1(matrix(m),1..2);
==> _[1,1]=x-y
==> _[1,2]=-z2+y
==> _[1,3]=y3-x+s
==> _[2,1]=x-y
==> _[2,2]=-z2+y
==> _[2,3]=y3-x+s
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See also:
nselect;
select.
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