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7.7.21.0. extendWeyl
Procedure from library dmodloc.lib (see dmodloc_lib).

Usage:
extendWeyl(S); S string or list of strings

Assume:
The basering is the n-th Weyl algebra over a field of characteristic 0 and for all 1<=i<=n the identity
var(i+n)*var(i)=var(i)*var(i+1)+1 holds, i.e. the sequence of variables is given by x(1),...,x(n),D(1),...,D(n), where D(i) is the differential operator belonging to x(i).

Return:
ring, Weyl algebra extended by vars given by S

Example:
 
LIB "dmodloc.lib";
ring @D2 = 0,(x,y,Dx,Dy),dp;
def D2 = Weyl();
setring D2;
def D3 = extendWeyl("t");
setring D3; D3;
==> //   characteristic : 0
==> //   number of vars : 6
==> //        block   1 : ordering dp
==> //                  : names    t x y Dt Dx Dy
==> //        block   2 : ordering C
==> //   noncommutative relations:
==> //    Dtt=t*Dt+1
==> //    Dxx=x*Dx+1
==> //    Dyy=y*Dy+1
list L = "u","v";
def D5 = extendWeyl(L);
setring D5;
D5;
==> //   characteristic : 0
==> //   number of vars : 10
==> //        block   1 : ordering dp
==> //                  : names    u v t x y Du Dv Dt Dx Dy
==> //        block   2 : ordering C
==> //   noncommutative relations:
==> //    Duu=u*Du+1
==> //    Dvv=v*Dv+1
==> //    Dtt=t*Dt+1
==> //    Dxx=x*Dx+1
==> //    Dyy=y*Dy+1