[SR-3127] Decimal should have accessors to convert to other numeric types

[lilyball]

Previous ID	SR-3127
Radar	None
Original Reporter	@lilyball
Type	Improvement

Additional Detail from JIRA

Votes	1
Component/s	Foundation
Labels	Improvement
Assignee	None
Priority	Medium

md5: 5c2629f75730480cb769435605c53f2d

is duplicated by:

• SR-4396 Decimal.doubleValue should be public

Issue Description:

Decimal should have accessors to produce Int, Int64, and Double values. These accessors should behave similarly to NSDecimalNumber's accessors (ideally they would produce the same values, though it's questionable whether the behavior of NSDecimalNumber is ideal for out-of-range integers). Possibly the integral accessors should return optionals (representing out-of-range numbers; in-range floating-point numbers should just truncate).

[belkadan]

I wonder if these make more sense as properties or methods on Decimal or as initializers on the target types.

[lilyball]

I'd suggest initializers on the other types, because that's how other numeric conversions work.