Offers a port of fractional indexing functionality, allowing generation of ordered indices between existing ones, ensuring consistent output. Supports generating multiple fractional indices simultaneously.
Based on Implementing Fractional Indexing by David Greenspan.
This port is based on the rocicorp/fractional-indexing repo and is meant to give the same output for any given input, but no guarantees are made that this port is 100% accurate to the original JavaScript source code it was ported from.
This is compatible with Kotlin Multiplatform as it makes use of only the Kotlin standard library (no JVM-specific code).
You can add this library as a dependency in Gradle in a Kotlin or Kotlin Multiplatform project:
dependencies {
// ...
implementation("com.davidarvelo:fractional-indexing:${latestVersion}")
}
rocicorp for the original code implemented in JavaScript, located at https://github.com/rocicorp/fractional-indexing, and ported to Kotlin in this repo.
class Usages {
fun generateFractionalIndexBetween() {
val first = FractionalIndexing.generateFractionalIndexBetween(null, null); // "a0"
// Insert after 1st
val second = FractionalIndexing.generateFractionalIndexBetween(first, null); // "a1"
// Insert after 2nd
val third = FractionalIndexing.generateFractionalIndexBetween(second, null); // "a2"
// Insert before 1st
val zeroth = FractionalIndexing.generateFractionalIndexBetween(null, first); // "Zz"
// Insert in between 2nd and 3rd (midpoint)
val secondAndHalf = FractionalIndexing.generateFractionalIndexBetween(second, third); // "a1V"
val beforeZeroth = FractionalIndexing.generateFractionalIndexBetween(null, zeroth)
println(first)
println(second)
println(third)
println(zeroth)
println(secondAndHalf)
println(beforeZeroth)
}
fun generateNFractionalIndicesBetween() {
val (first, second) = FractionalIndexing.generateNFractionalIndicesBetween(null, null, 2); // ['a0', 'a1']
// Insert after 2nd
val nextSet = FractionalIndexing.generateFractionalIndexBetween(second, null); // "a2"
// Insert two keys after 2nd
val (secondAgain, third) = FractionalIndexing.generateNFractionalIndicesBetween(second, null, 2); // ['a2', 'a3']
// Insert two keys before 1st
val twoMore = FractionalIndexing.generateNFractionalIndicesBetween(null, first, 2); // ['Zy', 'Zz']
// Insert two keys in between 1st and 2nd (midpoints)
val betweenKeys = FractionalIndexing.generateNFractionalIndicesBetween(first, second, 2); // ['a0G', 'a0V']
println("$first, $second")
println(nextSet)
println("$secondAgain, $third")
println(twoMore)
println(betweenKeys)
}
}
fun main() {
Usages().generateFractionalIndexBetween()
Usages().generateNFractionalIndicesBetween()
}
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