"Source: Text/Commut/RngDiff.text";
"Line: 3257";
"Date: Thu Sep 25 14:47:46 2025";
"Main: Fri Sep 26 14:29:19 2025";
// original file: Text/Commut/RngDiff.text, line: 3257
// Example: H121E57 ()
print "Example: H121E57";
ei := GetEchoInput();
SetEchoInput(true);
S<t> := DifferentialLaurentSeriesRing(Rationals());
R<D> := DifferentialOperatorRing(S);
IsRegularSingularOperator(D^2 -t*D+2);
assert $1;
IsRegularSingularOperator(D^2 +3);
assert $1;
IsRegularSingularOperator(D^2 +3 +O(t));
assert $1;
IsRegularSingularOperator(D^2 +3*t^(-1));
assert not $1;
SetEchoInput(ei);
