Best practices for ranges

[Sean Farrow]

Hi,

 

I’m in a situation where I need to ensure an instant is within range when validating arguments to a method.

 

What is the best practice for this:

To include both the minimum and maximum values, or have a half-open range excluding one value.

I’m looking to make this reusable using PostSharp, so would be interested as to what other people have done.

 

Thanks,

Sean

[Jon Skeet]

For instant ranges, I would definitely use "include minimum, exclude maximum" - which is exactly what the Interval type already encapsulates.

Date ranges are different - they'd typically include both ends.

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[Sean Farrow]

Hi,

 

Is there a reason the Instant.IsValid method and the Instant.MinValue/Instant.MaxValue are all internal?

It seems like these would be useful methods/fields to have exposed publicly.

Thanks,

Sean

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[Jon Skeet]

The Instant.MaxValue and Instant.MinValue properties are public.

IsValid isn't relevant externally, as users never "see" invalid instants - invalid instants are outside the normal range, and are used for special internal scenarios.

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[Sean Farrow]

Sorry, my fault, I meant Instant.BeforeMinValue.

Essentially, I need to create an instant that is completely invalid and is before the MinValue.

I would like not to have to use reflection. Is there anything in the testing assembly to do this?

Thanks,

Sean.

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[Jon Skeet]

You can't do that, basically - and you shouldn't use reflection to get at those invalid values. Noda Time is not written to support that use case. Invalid instants are purely intended for internal convenience. If you want to indicate "either a valid Instant, or nothing" you should  use Nullable<Instant>.

(If you do decide to use reflection, I make absolutely no guarantees of consistent behaviour between releases. You're basically going out of documented, supported behaviour at that point.)

Jon

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