Why is multiple inheritance not supported in most of programming language?

Question

Why is multiple inheritance not supported in most of programming language?

I could really use this feature to develop different layout of application?

Answer 1

One reason not to support it is ambiguity of method resolution.

http://en.wikipedia.org/wiki/Diamond_problem

However, I'm not sure what you mean by "most" programming languages. Many that are in use today support it directly (C++, Python, Perl, OCaml) or have a mechanism for similar functionality (Ruby and Scala come to mind).

Answer 2

Multiple inheritance is useful in many situations as a developer, but it greatly increases the complexity of the language, which makes life harder for both the compiler developers and the programmers.

• One problem occurs when two parent classes have data members or methods of the same name. It is difficult to resolve which is being referenced by the sub-class.

• Another occurs when two parent classes inherit from the same base class, forming a "diamond" pattern in the inheritance hierarchy.

• The order that the initialisation/elaboration of the parent classes needs to be specified - this can sometimes lead to behaviour changing when the order of the inheritance changes - something may catch developers by surprise.

• Some languages support a reference to 'super', or equivalent, which refers to an attribute of the base class for this object. That becomes difficult to support in a language with multiple inheritance.

• Some languages attempt to provide an automatic Object-Relational Model, so the objects can be made persistent with a regular RDMS. This mapping is difficult at the best of times (it has been described as the "Vietnam War" of software development), but it is much more difficult if multiple inheritance is supported.