Ada Nested Generic Package

Question

I tried searching a lot for what I thought was Nested Generic Packages, which I don't know how to implement in Ada. I found no helpful references or sources online of what I am trying to accomplish so please tell me if it's possible or other ways to accomplish it.

package AdjList is new List(Integer);
package Graph is new List(AdjList);

I am getting compilation errors for these 2 lines regarding the type I am passing to the List generic package.

I am trying to have 2 nested lists which will form a type of graph and I am forced to use this implementation approach. Any ideas/thoughts?

Answer 1

The error comes from the fact that you are passing AdjList, which is a package to the parameter. You need to pass a type that is the main data of that package.

package AdjList is new List(Integer);
package Graph is new List(AdjList.Data);   

Answer 2

Depending on the compiler/how you have set up your development environment, you may want to make sure each of the package instantiations are in separate file (.ads files if you are using Gnat).