Comparator for Pair in Kotlin
I can write comparator for specialized types in Kotlinclass Comparator() : kotlin.Comparator<Pair<Double, Int>>
But how can I write comparator using generics for all possible types that extend Comparable<...>?
generics kotlin comparator
asked Nov 22 at 19:51
Alex Row
337
add a comment |
I can write comparator for specialized types in Kotlinclass Comparator() : kotlin.Comparator<Pair<Double, Int>>
But how can I write comparator using generics for all possible types that extend Comparable<...>?
generics kotlin comparator
asked Nov 22 at 19:51
Alex Row
337
2
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57
add a comment |
I can write comparator for specialized types in Kotlinclass Comparator() : kotlin.Comparator<Pair<Double, Int>>
But how can I write comparator using generics for all possible types that extend Comparable<...>?
generics kotlin comparator
asked Nov 22 at 19:51
Alex Row
337
I can write comparator for specialized types in Kotlinclass Comparator() : kotlin.Comparator<Pair<Double, Int>>
But how can I write comparator using generics for all possible types that extend Comparable<...>?
generics kotlin comparator
generics kotlin comparator
asked Nov 22 at 19:51
Alex Row
337
asked Nov 22 at 19:51
Alex Row
337
asked Nov 22 at 19:51
Alex Row
337
asked Nov 22 at 19:51
Alex Row
337
asked Nov 22 at 19:51
Alex Row
337
337
2
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57
add a comment |
2
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57
2
2
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57
add a comment |
2 Answers
2
active
oldest
votes
You can create comparator, using helping functions - compareBy, compareByDescending, naturalOrder, reverseOrder https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/index.html
For example:
val map = mapOf<Int, String>()
// ... add values to the map
val sortedMap: SortedMap<Int, String> = map.toSortedMap(compareByDescending { it })
And for your case:
val comparator = compareBy<Pair<Double, Int>> { it.first }
Custom comparator:
class CustomComparator<T: Comparable<T>> : Comparator<T> {
override fun compare(o1: T, o2: T): Int {
return o1.compareTo(o2)
}
}
answered Nov 22 at 20:02
Sergey
1,97621324
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
WhycompareByand other helper functions don't work for you? You can use it to createComparatorof any Pairs.
– Sergey
Nov 23 at 7:54
add a comment |
You can use the following function to combine two comparators into a pair comparator which compares the first value of a pair with the first comparator and then the second value with the second comparator:
fun <T, U> pairComparator(
firstComparator: Comparator<T>,
secondComparator: Comparator<U>
): Comparator<Pair<T, U>> =
compareBy(firstComparator) { p: Pair<T, U> -> p.first }
.thenBy(secondComparator) { p: Pair<T, U> -> p.second }
Then you use it as following:
val source = listOf(1 to 2.3, 1 to 2.0, 0 to 3.0)
val result1 = source.sortedWith(pairComparator(naturalOrder(), naturalOrder()))
println(result1) // [(0, 3.0), (1, 2.0), (1, 2.3)]
val result2 = source.sortedWith(pairComparator(naturalOrder(), reverseOrder()))
println(result2) // [(0, 3.0), (1, 2.3), (1, 2.0)]
See the full code here: https://pl.kotl.in/BkMOzb8CX
answered Nov 23 at 22:43
Ilya
8,96943056
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You can create comparator, using helping functions - compareBy, compareByDescending, naturalOrder, reverseOrder https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/index.html
For example:
val map = mapOf<Int, String>()
// ... add values to the map
val sortedMap: SortedMap<Int, String> = map.toSortedMap(compareByDescending { it })
And for your case:
val comparator = compareBy<Pair<Double, Int>> { it.first }
Custom comparator:
class CustomComparator<T: Comparable<T>> : Comparator<T> {
override fun compare(o1: T, o2: T): Int {
return o1.compareTo(o2)
}
}
answered Nov 22 at 20:02
Sergey
1,97621324
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
WhycompareByand other helper functions don't work for you? You can use it to createComparatorof any Pairs.
– Sergey
Nov 23 at 7:54
add a comment |
You can create comparator, using helping functions - compareBy, compareByDescending, naturalOrder, reverseOrder https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/index.html
For example:
val map = mapOf<Int, String>()
// ... add values to the map
val sortedMap: SortedMap<Int, String> = map.toSortedMap(compareByDescending { it })
And for your case:
val comparator = compareBy<Pair<Double, Int>> { it.first }
Custom comparator:
class CustomComparator<T: Comparable<T>> : Comparator<T> {
override fun compare(o1: T, o2: T): Int {
return o1.compareTo(o2)
}
}
answered Nov 22 at 20:02
Sergey
1,97621324
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
WhycompareByand other helper functions don't work for you? You can use it to createComparatorof any Pairs.
– Sergey
Nov 23 at 7:54
add a comment |
You can create comparator, using helping functions - compareBy, compareByDescending, naturalOrder, reverseOrder https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/index.html
For example:
val map = mapOf<Int, String>()
// ... add values to the map
val sortedMap: SortedMap<Int, String> = map.toSortedMap(compareByDescending { it })
And for your case:
val comparator = compareBy<Pair<Double, Int>> { it.first }
Custom comparator:
class CustomComparator<T: Comparable<T>> : Comparator<T> {
override fun compare(o1: T, o2: T): Int {
return o1.compareTo(o2)
}
}
answered Nov 22 at 20:02
Sergey
1,97621324
You can create comparator, using helping functions - compareBy, compareByDescending, naturalOrder, reverseOrder https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/index.html
For example:
val map = mapOf<Int, String>()
// ... add values to the map
val sortedMap: SortedMap<Int, String> = map.toSortedMap(compareByDescending { it })
And for your case:
val comparator = compareBy<Pair<Double, Int>> { it.first }
Custom comparator:
class CustomComparator<T: Comparable<T>> : Comparator<T> {
override fun compare(o1: T, o2: T): Int {
return o1.compareTo(o2)
}
}
answered Nov 22 at 20:02
Sergey
1,97621324
edited Nov 22 at 20:21
answered Nov 22 at 20:02
Sergey
1,97621324
answered Nov 22 at 20:02
Sergey
1,97621324
answered Nov 22 at 20:02
Sergey
1,97621324
1,97621324
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
WhycompareByand other helper functions don't work for you? You can use it to createComparatorof any Pairs.
– Sergey
Nov 23 at 7:54
add a comment |
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
WhycompareByand other helper functions don't work for you? You can use it to createComparatorof any Pairs.
– Sergey
Nov 23 at 7:54
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
That's good, but I wanted for some implementation of generic class which can be used, for example, both for Pair<Int, String> and for Pair<Long, Double>
– Alex Row
Nov 22 at 21:46
Why
compareBy and other helper functions don't work for you? You can use it to create Comparator of any Pairs.– Sergey
Nov 23 at 7:54
Why
compareBy and other helper functions don't work for you? You can use it to create Comparator of any Pairs.– Sergey
Nov 23 at 7:54
add a comment |
You can use the following function to combine two comparators into a pair comparator which compares the first value of a pair with the first comparator and then the second value with the second comparator:
fun <T, U> pairComparator(
firstComparator: Comparator<T>,
secondComparator: Comparator<U>
): Comparator<Pair<T, U>> =
compareBy(firstComparator) { p: Pair<T, U> -> p.first }
.thenBy(secondComparator) { p: Pair<T, U> -> p.second }
Then you use it as following:
val source = listOf(1 to 2.3, 1 to 2.0, 0 to 3.0)
val result1 = source.sortedWith(pairComparator(naturalOrder(), naturalOrder()))
println(result1) // [(0, 3.0), (1, 2.0), (1, 2.3)]
val result2 = source.sortedWith(pairComparator(naturalOrder(), reverseOrder()))
println(result2) // [(0, 3.0), (1, 2.3), (1, 2.0)]
See the full code here: https://pl.kotl.in/BkMOzb8CX
answered Nov 23 at 22:43
Ilya
8,96943056
add a comment |
You can use the following function to combine two comparators into a pair comparator which compares the first value of a pair with the first comparator and then the second value with the second comparator:
fun <T, U> pairComparator(
firstComparator: Comparator<T>,
secondComparator: Comparator<U>
): Comparator<Pair<T, U>> =
compareBy(firstComparator) { p: Pair<T, U> -> p.first }
.thenBy(secondComparator) { p: Pair<T, U> -> p.second }
Then you use it as following:
val source = listOf(1 to 2.3, 1 to 2.0, 0 to 3.0)
val result1 = source.sortedWith(pairComparator(naturalOrder(), naturalOrder()))
println(result1) // [(0, 3.0), (1, 2.0), (1, 2.3)]
val result2 = source.sortedWith(pairComparator(naturalOrder(), reverseOrder()))
println(result2) // [(0, 3.0), (1, 2.3), (1, 2.0)]
See the full code here: https://pl.kotl.in/BkMOzb8CX
answered Nov 23 at 22:43
Ilya
8,96943056
add a comment |
You can use the following function to combine two comparators into a pair comparator which compares the first value of a pair with the first comparator and then the second value with the second comparator:
fun <T, U> pairComparator(
firstComparator: Comparator<T>,
secondComparator: Comparator<U>
): Comparator<Pair<T, U>> =
compareBy(firstComparator) { p: Pair<T, U> -> p.first }
.thenBy(secondComparator) { p: Pair<T, U> -> p.second }
Then you use it as following:
val source = listOf(1 to 2.3, 1 to 2.0, 0 to 3.0)
val result1 = source.sortedWith(pairComparator(naturalOrder(), naturalOrder()))
println(result1) // [(0, 3.0), (1, 2.0), (1, 2.3)]
val result2 = source.sortedWith(pairComparator(naturalOrder(), reverseOrder()))
println(result2) // [(0, 3.0), (1, 2.3), (1, 2.0)]
See the full code here: https://pl.kotl.in/BkMOzb8CX
answered Nov 23 at 22:43
Ilya
8,96943056
You can use the following function to combine two comparators into a pair comparator which compares the first value of a pair with the first comparator and then the second value with the second comparator:
fun <T, U> pairComparator(
firstComparator: Comparator<T>,
secondComparator: Comparator<U>
): Comparator<Pair<T, U>> =
compareBy(firstComparator) { p: Pair<T, U> -> p.first }
.thenBy(secondComparator) { p: Pair<T, U> -> p.second }
Then you use it as following:
val source = listOf(1 to 2.3, 1 to 2.0, 0 to 3.0)
val result1 = source.sortedWith(pairComparator(naturalOrder(), naturalOrder()))
println(result1) // [(0, 3.0), (1, 2.0), (1, 2.3)]
val result2 = source.sortedWith(pairComparator(naturalOrder(), reverseOrder()))
println(result2) // [(0, 3.0), (1, 2.3), (1, 2.0)]
See the full code here: https://pl.kotl.in/BkMOzb8CX
answered Nov 23 at 22:43
Ilya
8,96943056
answered Nov 23 at 22:43
Ilya
8,96943056
answered Nov 23 at 22:43
Ilya
8,96943056
answered Nov 23 at 22:43
Ilya
8,96943056
8,96943056
add a comment |
add a comment |
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2
kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/…
– JB Nizet
Nov 22 at 19:57