Zero-element

In a few cases you would need to define the function that return a Zero element. Zero element is the element which has the following features:

1. The sum or subtraction with zero zero of some element remain value unchanged.
2. Multiplication by zero makes zero.
3. Division by zero is not defined.

Sample type has ZeroSample constant defined, all numeric value has their usual zero values which can be used for that purpose.

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