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Fixed valuesAreComparable() and tests #1089

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Merged
merged 1 commit into from
Mar 7, 2025
Merged

Fixed valuesAreComparable() and tests #1089

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24 changes: 14 additions & 10 deletions core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/DataColumnType.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,6 @@ import org.jetbrains.kotlinx.dataframe.columns.ColumnGroup
import org.jetbrains.kotlinx.dataframe.columns.ColumnKind
import org.jetbrains.kotlinx.dataframe.columns.FrameColumn
import org.jetbrains.kotlinx.dataframe.columns.ValueColumn
import org.jetbrains.kotlinx.dataframe.impl.isNothing
import org.jetbrains.kotlinx.dataframe.impl.projectTo
import org.jetbrains.kotlinx.dataframe.type
import org.jetbrains.kotlinx.dataframe.typeClass
import org.jetbrains.kotlinx.dataframe.util.IS_COMPARABLE
Expand All @@ -21,8 +19,11 @@ import kotlin.contracts.contract
import kotlin.reflect.KClass
import kotlin.reflect.KType
import kotlin.reflect.KTypeProjection
import kotlin.reflect.KVariance
import kotlin.reflect.full.createType
import kotlin.reflect.full.isSubclassOf
import kotlin.reflect.full.isSubtypeOf
import kotlin.reflect.full.withNullability
import kotlin.reflect.typeOf

public fun AnyCol.isColumnGroup(): Boolean {
Expand Down Expand Up @@ -62,21 +63,24 @@ public fun AnyCol.isList(): Boolean = typeClass == List::class
public fun AnyCol.isComparable(): Boolean = valuesAreComparable()

/**
* Returns `true` if [this] column is inter-comparable, i.e.
* Returns `true` if [this] column is intra-comparable, i.e.
* its values can be compared with each other and thus ordered.
*
* If true, operations like [`min()`][AnyCol.min], [`max()`][AnyCol.max], [`median()`][AnyCol.median], etc.
* will work.
*
* Technically, this means the values' common type is a subtype of [Comparable] with
* the type argument not being [Nothing].
* Technically, this means the values' common type `T(?)` is a subtype of [Comparable]`<in T>(?)`
*/
public fun AnyCol.valuesAreComparable(): Boolean =
isSubtypeOf<Comparable<*>?>() &&
type().projectTo(Comparable::class).arguments[0].let {
it != KTypeProjection.STAR &&
it.type?.isNothing != true
}
isValueColumn() &&
isSubtypeOf(
Comparable::class.createType(
arguments = listOf(
KTypeProjection(KVariance.IN, type().withNullability(false)),
),
nullable = hasNulls(),
),
)

@PublishedApi
internal fun AnyCol.isPrimitive(): Boolean = typeClass.isPrimitive()
Expand Down
23 changes: 21 additions & 2 deletions core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTests.kt
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Expand Up @@ -2462,13 +2462,32 @@ class DataFrameTests : BaseTest() {
).toDataFrame()

df.int.valuesAreComparable() shouldBe true
df.comparableInt.valuesAreComparable() shouldBe true
// Comparable<Int> is not comparable to Comparable<Int>
df.comparableInt.valuesAreComparable() shouldBe false
df.string.valuesAreComparable() shouldBe true
df.comparableString.valuesAreComparable() shouldBe true
// Comparable<String> is not comparable to Comparable<String>
df.comparableString.valuesAreComparable() shouldBe false
df.comparableStar.valuesAreComparable() shouldBe false
df.comparableNothing.valuesAreComparable() shouldBe false
}

// https://github.com/Kotlin/dataframe/pull/1077#discussion_r1981352374
@Test
fun `values are comparable difficult`() {
val i = 1
val i1 = object : Comparable<Int> {
override fun compareTo(other: Int): Int = other

override fun toString(): String = "i1"
}
val col by columnOf(i, i1)

// We cannot calculate min/max for this column because Int does not implement Comparable<Comparable<Int>>
// aka i1.compareTo(i) would work but i.compareTo(i1) would not
dataFrameOf(col).max().isEmpty() shouldBe true
dataFrameOf(col).min().isEmpty() shouldBe true
}

@Test
fun `describe twice minimal`() {
val df = dataFrameOf("a", "b")(1, "foo", 3, "bar")
Expand Down