How to bind a slider to a parameter so that the slider allows the choice between values in a data column?

Suppose I have a column of data in Vega Lite, like a here, but larger: with 50 to 80 rows.

{
  "data": {
    "values": [
      {"a": "3.33"}, {"a": "3.36"}, {"a": "3.39"}, {"a": "3.42"}, {"a": "3.45"}, {"a": "3.48"},
      {"a": "3.51"}, {"a": "3.54"}, {"a": "3.57"}
    ]
  }

How to bind some parameter to a slider which would let the user interactively select which value from the column a should the parameter take?

I know that the following feature exists, but I would prefer not to use it because I already have the data in the column, and computing the range would be additional work:

{"input": "range", "min": 3.33,"max": 3.57,"step": 0.03}

Another reason that I want to avoid using a range is that (I think that) not all values would be accurately computed, because (I suppose that) Vega uses finite-precision floating point.

The following probably isn't relevant; but I'm using Vega Lite through the Julia VegaLite.jl interface.