operator + method
Performs addition with a nullable num value.
If both are Null, Null is returned.
If only one of them is Null, a non-null value is returned.
Nullableなnum値での加算を行います。
Implementation
num? operator +(num? other) {
if (this == null) {
return other;
}
if (other == null) {
return this;
}
return this! + other;
}