Language interoperability is the capability of two different

programming languages A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

to natively interact as part of the same system and operate on the same kind of data structures. There are many ways programming languages are interoperable with one another.

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaSc ...

, CSS, and

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

are interoperable as they are used in tandem in webpages. Some

object oriented Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of p ...

languages are interoperable thanks to their shared hosting

virtual machine In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized h ...

(e.g. .NET CLI compliant languages in the Common Language Runtime and JVM compliant languages in the Java Virtual Machine).

Methods for interoperability

Object models

Object models are standardised models which allow objects to be represented in a language-agnostic way, such that the same objects may be used across programs and across languages.

CORBA The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between s ...

and the COM are the most popular object models.

Virtual machines

(VM) is a specialised intermediate language that several different languages compile down to. Languages that use the same virtual machine can interoperate, as they will share a memory model and compiler and thus libraries from one language can be re-used for others on the same VM. VMs can incorporate type systems to ensure the correctness of participating languages and give languages a common ground for their type information. The use of an intermediate language during compilation or interpretation can provide more opportunities for optimisation.

Foreign function interfaces

Foreign function interfaces (FFI) allow programs written in one language to call functions written in another language. There are often considerations that preclude simply treating foreign functions as functions written in the host language, such as differences in types and execution model. Foreign function interfaces enable building wrapper libraries that provide functionality from a library from another language in the host language, often in a style that is more idiomatic for the language. Most languages have FFIs to C, which is the "lingua franca" of programming today.

Challenges

Object model differences

Object oriented languages attempt to pair containers of data with code, but how each language chooses how to do that may be slightly different. Those design decisions do not always map to other languages easily. For instance, classes using multiple inheritance from a language that permits it will not translate well to a language that does not permit multiple inheritance. A common approach to this issue is defining a subset of a language that is compatible with another language's features. This approach does mean in order for the code using features outside the subset to interoperate it will need to wrap some of its interfaces into classes that can be understood by the subset.

Memory models

Differences in how programming languages handle de-allocation of memory is another issue when trying create interoperability. Languages with automatic de-allocation will not interoperate well with those with manual de-allocation, and those with deterministic destruction will be incompatible with those with nondeterministic destruction. Based on the constraints of the language there are many different strategies for bridging the different behaviors. For example: C++ programs, which normally use manual de-allocation, could interoperate with a Java style garbage collector by changing de-allocation behavior to delete the object, but not reclaim the memory. This requires that each object will have to manually be de-allocated, in order for the garbage collector to release the memory safely.

Mutability

Mutability becomes an issue when trying to create interoperability between pure functional and procedural languages. Languages like

Haskell Haskell () is a general-purpose, statically-typed, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research and industrial applications, Haskell has pioneered a number of programming lan ...

have no mutable types, whereas C++ does not provide such rigorous guarantees. Many functional types when bridged to object oriented languages can not guarantee that the underlying objects won't be modified.

References

{{Reflist Programming languages