Take samples from generators

[jrwest]

Adds the ability to get or print samples from a generator. The visibility changes made to support this I believe to be safe because:

• allowing instantiation of BoundarySkewedDistribution shouldn't have negative consequences and can be helpful for debugging
• Precusor's constructor isn't exposed so a reference to it must obtained elsewhere (e.g. via BoundarySkewedDistribution) and then this change is just exposing the value that was generated (mutating that value isn't safe but this would also be only during some sort of debugging).

[hcoles]

Thanks for this, sorry for the very slow response.

Although I think this is useful functionality I'm not sure it should be pushed into the core Gen interface, I think it would make more sense as a utility that could be passed a Gen.

[jrwest]

Thanks for the reply! No worries at all.

Not opposed to moving it to an external/static interface. My only counter is that it adds extra characters to lines which can already be long (but static imports can resolve that).

For some reference to other libraries, Scalacheck and Hypothesis both define functions (sample/example) on their equivalent Gen interface. EQC has it in the Gen module but Erlang is a harder comparison because there are only module functions:

• ScalaCheck (Gen#sample)
• Hypothesis (.example())
• EQC sample