Re: packages with orphaned instances only

Ivan Lazar Miljenovic schrieb:

On 9 January 2011 07:20, Henning Thielemann wrote:

...

If there are multiple equally natural instances, then there should not be one at all.

It depends what you mean. In my case, I wanted the String instance for Arbitrary to follow certain rules (can't be the textual representation of a number, can't have certain characters in it, etc.).

This sounds like extra wishes that require a new type or some preprocessing within a quick check (e.g. filter out digits). You would not be happy with a private instance for Arbitrary String anyway, since different tests may have different requirements for the test strings (if not today, then maybe in future).