isBetween method
100.0.isBetween(50.0, 150.0) // true; 100.0.isBetween(100.0, 100.0) // true;
Implementation
bool isBetween(num first, num second) {
final lower = min(first, second);
final upper = max(first, second);
return this.validate() >= lower && this.validate() <= upper;
}