"Source: Text/Commut/RngDiff.text";
"Line: 1172";
"Date: Thu Sep 25 14:47:46 2025";
"Main: Fri Sep 26 14:29:19 2025";
// original file: Text/Commut/RngDiff.text, line: 1172
// Example: H121E21 ()
print "Example: H121E21";
ei := GetEchoInput();
SetEchoInput(true);
S<t>:=DifferentialLaurentSeriesRing(Rationals());
P<T> := PolynomialRing(Rationals());
Cext := ext<Rationals()|T^2+1>;
Sext<text>, mp := ConstantFieldExtension(S,Cext);
IsDifferentialLaurentSeriesRing(Sext);
assert $1;
ConstantRing(Sext) eq Cext;
assert $1;
Derivative(text^(-2)+7+2*text^3+O(text^6));
mp;
mp(t);
SetEchoInput(ei);
