Multiple inheritance

[3] Alternate methods of object composition not based on inheritance such as mixins and traits have also been proposed to address the ambiguity.

Languages that support multiple inheritance include: C++, Common Lisp (via Common Lisp Object System (CLOS)), EuLisp (via The EuLisp Object System TELOS), Curl, Dylan, Eiffel, Logtalk, Object REXX, Scala (via use of mixin classes), OCaml, Perl, POP-11, Python, R, Raku, and Tcl (built-in from 8.6 or via Incremental Tcl (Incr Tcl) in earlier versions[4][5]).

In this case, class A is at the top, both B and C separately beneath it, and D joins the two together at the bottom to form a diamond shape.

Typically these languages allow classes to implement multiple protocols, called interfaces in Java.

This strategy has been used by ActionScript, C#, D, Java, Nemerle, Object Pascal, Objective-C, Smalltalk, Swift and PHP.

With the introduction of default implementation for interfaces in Java 8 and C# 8, it is still possible to generate a Diamond Problem, although this will only appear as a compile-time error.