I really want to avoid calling `right.single { rec...

# general-advice

[groostav]

I really want to avoid calling right.single { record.name == target } , because if target comes from a loop thats a full cartesian product, and the data sets of left & right could be a thousand or so elements long

but they are ordered, so right[n] must have a record in left that occurs before right[n+1]

[CLOVIS]

So, this can't happen?

val left = listOf(
    CoolRecord("name1", emptyList()),
    CoolRecord("name2", emptyList()),
    CoolRecord("name3", emptyList()),
    CoolRecord("name4", emptyList())
)
val right = listOf(
    CoolRecord("name1", listOf(1.0, 2.0))
    CoolRecord("name4", listOf(5.0, 6.0))
)

[CLOVIS]

Are elements sorted by name in right ?

e.g. if I see name4 and I haven't yet seen name3 , can I assume it doesn't exist, or do I have to continue searching?

[groostav]

what you posted can happen, a variant that cant happen is

val left = listOf(
    CoolRecord("name1", emptyList()),
    CoolRecord("name2", emptyList()),
    CoolRecord("name3", emptyList()),
    CoolRecord("name4", emptyList())
)
val right = listOf(
    CoolRecord("name4" /*!!!*/, listOf(1.0, 2.0))
    CoolRecord("name1", listOf(5.0, 6.0))
)

[groostav]

the idea is that they are ordered the same, but the right is sparse

[Sam]

fun reallySlickJoinFunction(
  left: List<CoolRecord>,
  right: List<CoolRecord>
): List<CoolRecord> {
  var r = 0
  return left.map {
    if (it.name == right.getOrNull(r)?.name) right[r++] else it
  }
}