Add Compare method for duration and numeric objects.

[dpseidel]

Closes #695.

Let me know if you prefer to have the coercion go the other way, ie:

setMethod("Compare", signature(e1 = "Duration", e2 = "numeric"),
         function(e1, e2) {
            callGeneric(as.numeric(e1, "secs"), e2)
          })

Also will fix tidyverse/ggplot2#2414

[vspinu]

Tests need to be updated. Would be also nice if you could add a few more tests for this specific feature. Thanks!

[dpseidel]

Woops sorry about that -- tests are updated and new ones added. Documentation updated. Everything should be passing.

The existing comparison tests were not exactly were I was expecting so I ended up editing both test-ops-compare.r and test-durations.r. Let me know if you'd like them consolidated and where. Considering the method is in durations.r I would have expected the tests to live in test-durations.r but most were already in test-ops-compare.r so I added mine there.

[vspinu]

Sorry to still bug you on this, but I think as.duration is an unnecessary indirection here. You know that comparing to numeric means comparing seconds, so the numeric could be compared directly to e1@.Data as in the "character" method below.

I even think that an ANY method with as.numeric could be an even better solutions here. But it might have some unexpected consequences though.

[dpseidel]

No that's fine. Bug away. Let's get it right. Which do you prefer then? I could try the ANY solution with some tests but I think you're right there may be unforeseen problems caused by that.

[dpseidel]

For now, I've just changed the method to drop the unnecessary coercion and compare the @.Data instead. Makes much more sense.

[vspinu]

Thanks. Let's do this for now and I will think a bit more about ANY method. Most likely I won't implement it as it will create more room for bugs. For instance, you really don't want it to work on factors.