## Draft 3.1

* Narrow and clarify the behavior of `Calculation.clamp()` with
  potentially-multiple arguments.

* Make the argument type of `CalculationOperation.equals()` and
  `CalculationInterpolation.equals()` `unknown` to match the immutable.js
  typings.

* Rather than making each `SassCalculation` factory check transitively for
  quoted strings, make `CalculationOperation`'s constructor check for them so
  that they're guaranteed not to exist transitively.

## Draft 3

* Make `CalculationOperation` and `CalculationInterpolation` concrete rather
  than abstract classes.
* Export `CalculationValue` and `CalculationOperator` types.
* Adjust `SassCalculation.clamp` to interpret comma-separated `min` values as
  valid input for `value` and `max`.

## Draft 2

* Simplify calculations at the point at which they're returned from the JS API,
  rather than eagerly when they're constructed.

## Draft 1

* Initial draft.
