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D.2.6.2 changeord
Procedure from library ring.lib (see ring_lib).
- Usage:
changeord(newr,o[,r]); newr,o=strings, r=ring/qring
- Create:
create a new ring with name ‘newr‘ and make it the basering if r is an existing ring/qring [default: r=basering].
The new ring differs from the old ring only in the ordering. If, say, (newr,o) = ("R","wp(2,3),dp") and the ring r exists and has >=3 variables, the new basering will have name R and ordering wp(2,3),dp.- Return:
No return value
- Note:
This proc uses ’execute’ or calls a procedure using ’execute’. If you use it in your own proc, let the local names of your proc start with @.
Example:
LIB "ring.lib";
ring r=0,(x,y,u,v),(dp(2),ds);
changeord("R","wp(2,3),dp"); R; "";
→ // basering is now R
→ // characteristic : 0
→ // number of vars : 4
→ // block 1 : ordering wp
→ // : names x y
→ // : weights 2 3
→ // block 2 : ordering dp
→ // : names u v
→ // block 3 : ordering C
→
ideal i = x^2,y^2-u^3,v;
qring Q = std(i);
changeord("Q'","lp",Q); Q';
→ // basering is now Q'
→ // characteristic : 0
→ // number of vars : 4
→ // block 1 : ordering lp
→ // : names x y u v
→ // block 2 : ordering C
→ // quotient ring from ideal
→ _[1]=v
→ _[2]=x2
→ _[3]=y2-u3
kill R,Q,Q';
if(system("with","Namespaces")) {
if( nameof(Current) == "Ring" ) {
kill Top::R,Top::Q';
} else {
kill Ring::R,Ring::Q';
}
}
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