Add M.Q.Convert.DoubleAsStringWithFormat

[tcNickolas]

trafficstars

Is your feature request related to a problem? Please describe. I print arbitrary floating-point numbers that are arguments to the tests in the katas quite often, and printing them with the default ~15 digits of precision doesn't look particularly good, especially if there are multiple numbers and a narrow space to display the text. Here is the example from the published Single-Qubit Gates kata, task "Prepare Arbitrary State":

Describe the solution you'd like Bring back the function M.Q.Convert.DoubleAsStringWithFormat that used to be available in the classic QDK.

Describe alternatives you've considered I could modify some of the tests to use "neat" numbers, but that makes the code much more complicated unnecessarily, and sometimes I need specific numbers that I cannot round to 3-4 digits of precision.

[filipw]

I also ran into this problem.

I think in general it would be good to get some guidance on how display formatting of numerical values is supposed to be done in the new QDK.

[tcNickolas]

I have two possible suggestions for this API:

• Add M.Q.Convert.DoubleAsStringWithPrecision that would allow only to format a number with a specific number of decimal digits - that's enough for my purposes:

  function DoubleAsStringWithPrecision(a : Double, precision : Int) : String
  

• Add M.Q.Convert.DoubleAsStringWithFormat that would take a string second parameter with

  function DoubleAsStringWithFormat(a : Double, fmt : String) : String
  

  We used to rely on C#-style format strings, but since we've switched to Rust, I think it makes sense to use Rust format strings in this case instead.

Personally I like the first option more, it's more straightforward, and I can't think of a scenario where I'd use more complicated formatting. Thoughts?

[JPark1023]

I can work on this