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D.2.12.4 defring

Procedure from library ring.lib (see ring_lib).

Usage:
defring(ch,n,va,or); ch,va,or=strings, n=integer

Return:
ring R with characteristic 'ch', ordering 'or' and n variables with names derived from va.
If va is a single letter, say va="a", and if n<=26 then a and the following n-1 letters from the alphabet (cyclic order) are taken as variables. If n>26 or if va is a single letter followed by a bracket, say va="T(", the variables are T(1),...,T(n).

Note:
This proc is useful for defining a ring in a procedure. This proc uses 'execute' or calls a procedure using 'execute'.

Example:
 
LIB "ring.lib";
def r=defring("0",5,"u","ls"); r; setring r;"";
==> // coefficients: QQ
==> // number of vars : 5
==> //        block   1 : ordering ls
==> //                  : names    u v w x y
==> //        block   2 : ordering C
==> 
def R=defring("(2,A)",10,"x(","(dp(3),ws(1,2,3),ds)"); R; setring R;
==> // coefficients: ZZ/2(A)
==> // number of vars : 10
==> //        block   1 : ordering dp
==> //                  : names    x(1) x(2) x(3)
==> //        block   2 : ordering ws
==> //                  : names    x(4) x(5) x(6)
==> //                  : weights     1    2    3
==> //        block   3 : ordering ds
==> //                  : names    x(7) x(8) x(9) x(10)
==> //        block   4 : ordering C