org.eclipse.viatra.query.runtime.matchers.psystem.aggregations

## Annotation Type AggregatorType

-     @Target(value=TYPE)
       @Retention(value=RUNTIME)
       @Inherited
      public @interface AggregatorType

  The aggregator type annotation describes the type constraints for the selected aggregator. In version 1.4, two kinds of aggregators are supported:
  1. An aggregator that does not consider any parameter value from the call (`count`), just calculates the number of matches. This is represented by a single `Void` and a single corresponding return type.
  2. An aggregator that considers a single parameter from the call, and executes some aggregate operations over it. Such an aggregate operation can be defined over multiple types, where each possible parameter type has a corresponding return type declared.
  Important! The parameterTypes and returnTypes arrays must have
  - The same number of classes defined each.
  - Items are corresponded by index.
  - Items should represent data types
  Since:
    1.4

- - ### Required Element Summary

    Required Elements
    Modifier and Type | Required Element and Description
    --- | ---
    `java.lang.Class<?>[]` | `parameterTypes`
    `java.lang.Class<?>[]` | `returnTypes`

- - ### Element Detail

    - #### parameterTypes

          public abstract java.lang.Class<?>[] parameterTypes

  - - #### returnTypes

          public abstract java.lang.Class<?>[] returnTypes