have float factory take an optional :precision value

[kellyredding]

This would allow generating floats with a specific precision.

[kellyredding]

@jcredding do you remember why I put this issue in? I can't right now and stupidly didn't put any context into the issue or my dev notes.

I have something working for this but am not in love with it. Also, these are floating point numbers so exact values are a lie. Just b/c a value is 12.456 doesn't mean you can't express that same number in a higher precision and end up with 12.45599912345322.

My implementation looks like this:

Factory.float(13)                  #=> 12.6381341843036762
Factory.float(13, :precision => 2) #=> 10.12
Factory.float(:precision => 2)     #=> 95.79

I don't love the method signature but I have to account for both optionally passing a max value and optionally passing a precision value. Couple that with the float values are a lie bit above and I'm ver lukewarm on this (unless we have a good use-case for this).

Thanks for any help context.

[kellyredding]

@jcredding also the implementation looks something like this:

sprintf("%0.#{opts[:precision] || 16}f", (max || 100) * rand).to_f

(16 is the default precision used by rand, btw). Figured you should see this and weigh it when deciding)

[jcredding]

@kellyredding - I'm fine with adding this though I don't know of a good reason we'd need it currently. Maybe with much-decimal and only wanting to use random floats based on the precision used with much-decimal? I generally prefer testing with full random values (so don't set a precision) but other's might prefer having more "realistic" (it's unlikely someone enters a float with 16 digits) values.

As far as the implementation, I would have done the integer trick where you multiple it by 10^precision, convert to an integer, then divide by the 10^precision but that's more because I forget about sprintf. I don't have an issue with that implementation; no idea what's more performant but the sprintf seems like less work.

[kellyredding]

@jcredding I think I'm going to hold off on this for now. I just don't feel good adding it w/o a good use case. I'll keep this issue around with our notes for future reference if a use case does come up though. Cool?

[kellyredding]

(notes from last time I played with this)

      def self.float(*args)
        opts, max = [
          args.last.kind_of?(::Hash) ? args.pop : {},
          args.last
        ]
        sprintf("%0.#{opts[:precision] || 16}f", (max || 100) * rand).to_f
      end

    should "allow passing a precision value using `float`" do
      skip "TODO: test precision w/ and w/o max value"
    end