Is there no `until` function for `Float` in common...

# multiplatform

[eygraber]

Is there no until function for Float in common code?

[ephemient]

there is currently only a ClosedFloatingPointRange, which cannot support a half-open range

[ephemient]

Kotlin 1.8 will have a new `..<`/`rangeUntil` operator which returns a OpenEndRange, with support for floats

[ephemient]

I suppose you could do something like

infix fun Float.until(to: Float): ClosedFloatingPointRange<Float> = this .. when {
    to < 0f -> Float.fromBits(to.toBits() + 1)
    to > 0f -> Float.fromBits(to.toBits() - 1)
    to == 0f -> -Float.MIN_VALUE
    else -> to
}

in current/earlier Kotlin versions to produce the nearest closed range that contains everything the open range would

[ephemient]

(basically mirroring how Kotlin translates 0 until 3 into 0..2 on integers currently, except that we have to do a bit of bit manipulation to get the immediately prior floating point value)

[Michael Paus]

You could have also used the floating point ulp function here but I guess the bit fiddling may be even more efficient.

[ephemient]

ulp is the delta to the successor, not the prior, which is not necessarily the same

[ephemient]

e.g.

val x = 1f
val y = x - x.ulp
val z = Float.fromBits(1f.toBits() - 1)
y < z && z < x

so you can't actually use it to decrement the range end