Multimethod definition
Proper definition
Definition
An EVL multimethod is defined as follows:
- A multimethod of dimension D has a set M of N match methods mj with 0 <= j < N.
- The multimethod has a tuple of types uk of size NV called non-virtual parameter types.
- The multimethod has a return type R.
- For each match method mj:
- The first D parameter types is a tuple of types tj of size D called virtual parameter types.
- The following parameter types must be exactly the non-virtual parameter types defined above.
- An object of type R is returned or an object of type RA from which R is assignable. Otherwise an exception is thrown.
- There is optional data that can be used for solving ambiguities.
- The multimethod has a method comparator, that can be the symmetric, asymmetric or another distance comparator.
- The multimethod has a cache strategy.
Examples
Suppose we have a multimethod of dimension 2 with 3 non-virtual parameter types (String, int, boolean) and the return type int. The following match methods can be part of the multimethod or not:
| Match method | Accepted | Error |
|---|---|---|
| int m1(A, A, String, int, boolean) | yes | - |
| int m1(A, B, String, int) | no | bad number of non-virtual parameter types |
| int m1(D, C, String, float, boolean) | no | bad non-virtual parameter types |
| void m1(A, C, String, int, boolean) | no | bad return type |