sum
sum adds up all the values of a selected numeric property and returns the total sum as a Long
sum over List
import arrow.aql.extensions.list.select.*
import arrow.aql.extensions.list.where.*
import arrow.aql.extensions.list.sum.*
import arrow.aql.extensions.listk.select.selectAll
import arrow.aql.extensions.id.select.value
data class Student(val name: String, val age: Int)
val john = Student("John", 30)
val jane = Student("Jane", 32)
val jack = Student("Jack", 32)
fun main(args: Array<String>) {
//sampleStart
val result =
listOf(john, jane, jack).query {
selectAll() where { age > 30 } sum { age.toLong() }
}.value()
//sampleEnd
println(result)
}
sum works with any data type that provides an instance of Foldable<F> where F is the higher kinded representation of the data type. For example ForOption when targeting the Option<A> data type or ForListK when targeting the List<A> data type
Learn more about the AQL combinators
Supported Data types
| Module | Data types |
| arrow.core | Either, ListK, NonEmptyList, Option, SequenceK, Try |