The signature of a generic comparison function.
A comparison function represents an ordering on a type of objects. A total ordering on a type means that for two values, either they are equal or one is greater than the other (and the latter must then be smaller than the former).
A Comparator function represents such a total ordering by returning
a
is smaller than b
,a
is equal to b
, anda
is greater than b
.typedef Comparator<T> = int Function(T a, T b);
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https://api.dart.dev/stable/2.5.0/dart-core/Comparator.html