F# Floating point ranges are experimental and may be deprecated

Question

I\'m trying to make a little function to interpolate between two values with a given increment.

[ 1.0 .. 0.5 .. 20.0 ]

The compiler tells m

Answer 1

As Jon and others pointed out, floating point range expressions are not numerically robust. For example [0.0 .. 0.1 .. 0.3] equals [0.0 .. 0.1 .. 0.2]. Using Decimal or Int Types in the range expression is probably better.

For floats I use this function, it first increases the total range 3 times by the smallest float step. I am not sure if this algorithm is very robust now. But it is good enough for me to insure that the stop value is included in the Seq:

let floatrange start step stop =
    if step = 0.0 then  failwith "stepsize cannot be zero"
    let range = stop - start 
                |> BitConverter.DoubleToInt64Bits 
                |> (+) 3L 
                |> BitConverter.Int64BitsToDouble
    let steps = range/step
    if steps < 0.0 then failwith "stop value cannot be reached"
    let rec frange (start, i, steps) =
        seq { if i <= steps then 
                yield start + i*step
                yield! frange (start, (i + 1.0), steps) }
    frange (start, 0.0, steps)