operator - method
Implementation
Color operator -(dynamic v) {
if (v is double) {
return Color(r: r - v, g: g - v, b: b - v);
} else if (v is Color) {
return Color(r: r - v.r, g: g - v.g, b: b - v.b);
} else {
throw 'Color only support subtraction by double or Color';
}
}