anchor.diff:           let res1 = dt.Subtract(ts).Ticks
            let res2 = (dt - ts).Ticks
            if (res1 = res2)
  -         then float res2
  +         // TODO: Worrying that we need to round to 5 sig. figs. here. 
  +         //       Perhaps the number type in JS isn't precise enough for this implementation.
  +         then toSigFigs 5 (float res2)
            else failwith "synonyms don't match"
         @@>
   
  
positive.code:    check 
        <@@ 
           let dt = DateTime(2014,9,11).AddDays(v)
           float dt.Ticks
        @@>
  
  [<TestCase(100.); TestCase(-100.); TestCase(0.)>]
  
negative.code: 
  open NUnit.Framework
  open System
  
  [<FunScript.JS>]
  let toSigFigs nSigFigs x =
      let absX = abs x
      let digitsToStartOfNumber = floor(log10 absX) + 1. // x > 0 => +ve | x < 0 => -ve
      let digitsToAdjustNumberBy = int digitsToStartOfNumber - nSigFigs
      let scale = pown 10. digitsToAdjustNumberBy
      round(x / scale) * scale
  
  // TODO: These tests don't work with Jint, but the generated JS works fine in the browser
  //[<Test>]
  