Forsythe is the only language with intersection type (composite data types used to assign several types to an object) that is not actively developed.
He defined the programming languages Gedanken and Forsythe, known for its use of intersection types. Forsythe No C# Yes F# Ceylon Yes Yes Flow Yes Java Yes Scala Yes TypeScript Yes Whiley Yes Intersection types are composite data types. Similar to product types, they are used to assign several types to an object. 
