%YAML 1.2
---
scalar_functions:
  -
    name: "index_in"
    description: >
      Checks the membership of a value in a list of values

      Returns the first 0-based index value of some input `T` if `T` is equal to
      any element in `List<T>`.  Returns `NULL` if not found.

      If `T` is `NULL`, returns `NULL`.

      If `T` is `NaN`:
        - Returns 0-based index of `NaN` in `List<T>` (default)
        - Returns `NULL` (if `NAN_IS_NOT_NAN` is specified)
    impls:
      - args:
          - name: x
            value: T
          - name: y
            value: List<T>
        options:
          nan_equality:
            values: [ NAN_IS_NAN, NAN_IS_NOT_NAN ]
        nullability: DECLARED_OUTPUT
        return: int64?