In small doses, OOP is invaluable, especially for defining modules and their interfaces. Alas, OOP advocates, especially in the old days, oversold it. Several m

In small doses, OOP is invaluable, especially for defining modules and their interfaces. Alas, OOP advocates, especially in the old days, oversold it. Several major flaws: * "Everything is an object". This creates unnecessary confusion between data and modules and sometimes even functions. * "Everything is a message". This encourages splitting state between a myriad of objects, each hiding some tiny bit of mutable state that changes whenever it receives a message. Reasoning about such a state graph is impossible for any non-trivial application. * "Everything is an interface", which leads to tests tightly coupled to implementation due to mock over-usage. * "Everything is an inheritance hierarchy". Practice has proven that composition is better than inheritance.