Guarantees at compile time: Array<double> means the only element you will encounter is a double. Array<ISomeInterface> means the only element you will encount

Guarantees at compile time: Array<double> means the only element you will encounter is a double. Array<ISomeInterface> means the only element you will encounter is of type ISomeInterface. hence, you can express part of some code's requirements via the types that a function,class exposes and/or requires. these requirements can then be checked at compile time. without this you have to defer the "checking" to runtime.