StaDyn (programming language)

Last updated
StaDyn
StaDyn-logo.png
Paradigm Object oriented
Designed by Francisco Ortin [1]
Developer Computational Reflection research group [2] of the University of Oviedo
First appeared2007;17 years ago (2007)
Stable release
2.2.1 / 11 May 2022;2 years ago (2022-05-11)
Typing discipline Hybrid static and dynamic typing, gradual typing, strong, inferred
Implementation language C#
Platform Common Language Infrastructure (.NET Framework)
License MIT License [3]
Website reflection.uniovi.es/stadyn
Major implementations
C#
Influenced by
C#, OCaml, StrongTalk, Boo

StaDyn is an object-oriented general-purpose programming language for the .NET platform that supports both static and dynamic typing in the same programming language.

Contents

The StaDyn compiler gathers type information for the dynamically typed code. That type information is used to detect type errors at compilation time and to perform significant optimizations. For that purpose, it provides type reconstruction (inference), flow-sensitive types, union and intersection types, constraint-based typing, alias analysis and method specialization. Its first prototype appeared in 2007, as a modification of C# 3.0. Type inference was supported by including var as a new type, unlike C#, which only offers var to define initialized local variables. Flow-sensitive types of var references are inferred by the compiler, providing type-safe duck typing. [4] When a more lenient approach is required by the programmer, the dynamictype could be used instead of var. Although type inference is still performed, dynamic references behave closer to those in dynamic languages.

StaDyn is designed by Francisco Ortin [1] from the University of Oviedo. The language has been implemented by different members of the Computational Reflection research group, [2] including Miguel Garcia, Jose Baltasar García Perez-Schofield and Jose Quiroga, besides Francisco Ortin.

The name StaDyn is a portmanteau of static and dynamic, denoting its aim to provide the benefits of both static and dynamic typing.

Code samples

Variables with different types

Just like dynamic languages, variables may hold different types in the same scope:

usingSystem;classProgram{publicstaticvoidMain(){Console.Write("Number: ");varage=Console.In.ReadLine();Console.WriteLine("Digits: "+age.Length);age=Convert.ToInt32(age);age++;Console.WriteLine("Happy birthday, you are "+age+" years old now.");intlength=age.Length;// * Compiler error}}

The age variable is first inferred as string, so it is safe to get its Length property. Then, it holds an integer, so age++ is a valid expression. The compiler detects an error in the last line, since Length is no longer provided by age.

The generated code does not use a single Object variable to represent age, but two different variables whose types are string and int. This is achieved with a modification of the algorithm to compute the SSA form. [5] This makes the generated code to be more efficient, since runtime type conversions are not required.

Flow-sensitive types

var and dynamic variables can hold flow-sensitive types:

usingSystem;classProgram{publicstaticvoidMain(String[]args){varexception;if(args.Length>0)exception=newApplicationException("An application exception.");elseexception=newSystemException("A system exception.");Console.WriteLine(exception.Message);}}

It is safe to get the Message property from exception because both ApplicationException and SystemException provide that property. Otherwise, a compiler error is shown. In this way, StaDyn provides a type-safe static duck-typing system.

In the following program:

usingSystem;classProgram{publicstaticvoidMain(String[]args){varexception;switch(args.Length){case0:exception=newApplicationException("An application exception.");break;case1:exception=newSystemException("A system exception.");break;default:exception="This is not an exception.";break;}Console.WriteLine(exception.Message);// * Compiler error with var, but not with dynamicConsole.WriteLine(exception.Unknown);// * Compiler error}}

The Message property is not provided by String, so a compiler error is shown for exception.Message. However, if we declare exception as dynamic, the previous program is accepted by the compiler. dynamic is more lenient than var, following the flavor of dynamic languages. However, static type checking is still performed. This is shown in the last line of code, where the compiler shows an error for exception.Unknown even if exception is declared as dynamic. This is because neither of the three possible types (ApplicationException, SystemException and String) supports the Unknown message. [6]

Although dynamic and var types can be used explicitly to obtain safer or more lenient type checking, the dynamism of single var references can also be modified with command-line options, XML configuration files and a plugin for Visual Studio. [7]

Type inference of fields

var and dynamic types can be used as object fields:

classWrapper{privatevarattribute;publicWrapper(varattribute){this.attribute=attribute;}publicvarget(){returnattribute;}publicvoidset(varattribute){this.attribute=attribute;}}classTest{publicstaticvoidMain(){stringaString;intaInt;Wrapperwrapper=newWrapper("Hello");aString=wrapper.get();aInt=wrapper.get();// * Compiler errorwrapper.set(3);aString=wrapper.get();// * Compiler erroraInt=wrapper.get();}}

The Wrapper class can wrap any type. Each time we call the set method, the type of attribute is inferred as the type of the argument. Each object has a potentially different type of attribute, so its type is stored for every single instance rather than for the whole class. In this way, the two lines indicated in the code above report compilation errors. A type-based alias analysis algorithm is implemented to support this behavior. [8]

Constraint-based types

Let's analyze the following method:

publicstaticvarupper(varparameter){returnparameter.ToUpper();}

The type of parameter and the function return value are inferred by the compiler. To that aim, a constraint is added to the type of the upper method: the argument must provide a ToUpper method with no parameters. At each invocation, the constraint will be checked. Additionally, the return type of upper will be inferred as the return type of the corresponding ToUpper method implemented by the argument. [9]

The programmer may use either var or dynamic to declare parameter, changing the way type checking is performed upon method invocation. Let's assume that the argument passed to upper holds a flow-sensitive type (e.g., the ApplicationException, SystemException or Stringexception variable in the code above). With var, all the possible types of the argument must provide ToUpper; with dynamic, at least one type must provide ToUpper.

Runtime performance

The type information gathered by StaDyn is used to perform significant optimizations in the generated code: [10] the number of type inspections and type casts are reduced, reflection is avoided, frequent types are cached, and methods with constraints are specialized. The point of all the optimizations is to reduce the number of type-checking operations performed at runtime, which is the main performance penalty of most dynamic languages. Many of those type checks are undertaken earlier by the StaDyn compiler. A detailed evaluation of the runtime performance of StaDyn is detailed in. [4]

See also

Related Research Articles

In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every term. Usually the terms are various language constructs of a computer program, such as variables, expressions, functions, or modules. A type system dictates the operations that can be performed on a term. For variables, the type system determines the allowed values of that term.

Type inference, sometimes called type reconstruction, refers to the automatic detection of the type of an expression in a formal language. These include programming languages and mathematical type systems, but also natural languages in some branches of computer science and linguistics.

In computer science, boxing is the transformation of placing a primitive type within an object so that the value can be used as a reference. Unboxing is the reverse transformation of extracting the primitive value from its wrapper object. Autoboxing is the term for automatically applying boxing and/or unboxing transformations as needed.

In computer science, type safety and type soundness are the extent to which a programming language discourages or prevents type errors. Type safety is sometimes alternatively considered to be a property of facilities of a computer language; that is, some facilities are type-safe and their usage will not result in type errors, while other facilities in the same language may be type-unsafe and a program using them may encounter type errors. The behaviors classified as type errors by a given programming language are usually those that result from attempts to perform operations on values that are not of the appropriate data type, e.g., adding a string to an integer when there's no definition on how to handle this case. This classification is partly based on opinion.

This article compares two programming languages: C# with Java. While the focus of this article is mainly the languages and their features, such a comparison will necessarily also consider some features of platforms and libraries.

<span class="mw-page-title-main">Java syntax</span> Set of rules defining correctly structured program

The syntax of Java is the set of rules defining how a Java program is written and interpreted.

<span class="mw-page-title-main">C Sharp (programming language)</span> Programming language

C# is a general-purpose high-level programming language supporting multiple paradigms. C# encompasses static typing, strong typing, lexically scoped, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines.

Platform Invocation Services, commonly referred to as P/Invoke, is a feature of Common Language Infrastructure implementations, like Microsoft's Common Language Runtime, that enables managed code to call native code.

<span class="mw-page-title-main">Oxygene (programming language)</span> Object Pascal-based programming language

Oxygene is a programming language developed by RemObjects Software for Microsoft's Common Language Infrastructure, the Java Platform and Cocoa. Oxygene is based on Delphi's Object Pascal, but also has influences from C#, Eiffel, Java, F# and other languages.

Haxe is a high-level cross-platform programming language and compiler that can produce applications and source code for many different computing platforms from one code-base. It is free and open-source software, released under an MIT License. The compiler, written in OCaml, is released under the GNU General Public License (GPL) version 2.

C++11 is a version of a joint technical standard, ISO/IEC 14882, by the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC), for the C++ programming language. C++11 replaced the prior version of the C++ standard, named C++03, and was later replaced by C++14. The name follows the tradition of naming language versions by the publication year of the specification, though it was formerly named C++0x because it was expected to be published before 2010.

Generics are a facility of generic programming that were added to the Java programming language in 2004 within version J2SE 5.0. They were designed to extend Java's type system to allow "a type or method to operate on objects of various types while providing compile-time type safety". The aspect compile-time type safety required that parametrically polymorphic functions are not implemented in the Java virtual machine, since type safety is impossible in this case.

Anonymous types are a feature of C# 3.0, Visual Basic .NET 9.0, Oxygene, Scala and Go that allows data types to encapsulate a set of properties into a single object without having to first explicitly define a type. This is an important feature for the SQL-like LINQ feature that is integrated into C# and VB.net. Since anonymous types do not have a named type, they must be stored in variables declared using the var keyword, telling the C# compiler to use type inference for the variable. The properties created are read-only in C#, however, they are read-write in VB.net.

This article describes the syntax of the C# programming language. The features described are compatible with .NET Framework and Mono.

Cobra is a discontinued general-purpose, object-oriented programming language. Cobra is designed by Charles Esterbrook, and runs on the Microsoft .NET and Mono platforms. It is strongly influenced by Python, C#, Eiffel, Objective-C, and other programming languages. It supports both static and dynamic typing. It has support for unit tests and contracts. It has lambda expressions, closures, list comprehensions, and generators.

In computer science, manifest typing is explicit identification by the software programmer of the type of each variable being declared. For example: if variable X is going to store integers then its type must be declared as integer. The term "manifest typing" is often used with the term latent typing to describe the difference between the static, compile-time type membership of the object and its run-time type identity.

The programming language C# version 3.0 was released on 19 November 2007 as part of .NET Framework 3.5. It includes new features inspired by functional programming languages such as Haskell and ML, and is driven largely by the introduction of the Language Integrated Query (LINQ) pattern to the Common Language Runtime. It is not currently standardized by any standards organisation.

Nemerle is a general-purpose, high-level, statically typed programming language designed for platforms using the Common Language Infrastructure (.NET/Mono). It offers functional, object-oriented, aspect-oriented, reflective and imperative features. It has a simple C#-like syntax and a powerful metaprogramming system.

Swift is a high-level general-purpose, multi-paradigm, compiled programming language created by Chris Lattner in 2010 for Apple Inc. and maintained by the open-source community. Swift compiles to machine code and uses an LLVM-based compiler. Swift was first released in June 2014 and the Swift toolchain has shipped in Xcode since Xcode version 6, released in September 2014.

<span class="mw-page-title-main">Nim (programming language)</span> Programming language

Nim is a general-purpose, multi-paradigm, statically typed, compiled high-level system programming language, designed and developed by a team around Andreas Rumpf. Nim is designed to be "efficient, expressive, and elegant", supporting metaprogramming, functional, message passing, procedural, and object-oriented programming styles by providing several features such as compile time code generation, algebraic data types, a foreign function interface (FFI) with C, C++, Objective-C, and JavaScript, and supporting compiling to those same languages as intermediate representations.

References

  1. 1 2 "Francisco Ortin". uniovi.es. Retrieved May 17, 2022.
  2. 1 2 "Computational Reflection Research Group". uniovi.es. Retrieved May 17, 2022.
  3. ↑ "StaDyn Download". uniovi.es. Retrieved May 17, 2022.
  4. 1 2 Francisco Ortin; Miguel Garcia; Sean McSweeney (2019). "Rule-based program specialization to optimize gradually typed code". Knowledge-Based Systems. 179: 145–173. doi:10.1016/j.knosys.2019.05.013. hdl: 10651/53505 . S2CID   182002303.
  5. ↑ Jose Quiroga; Francisco Ortin (2017). "SSA Transformations to Facilitate Type Inference in Dynamically Typed Code". The Computer Journal. doi:10.1093/comjnl/bxw108.
  6. ↑ Francisco Ortin; Miguel Garcia (2011). "Union and intersection types to support both dynamic and static typing". Information Processing Letters. 111 (6): 278–286. doi:10.1016/j.ipl.2010.12.006. hdl: 10651/8732 .
  7. ↑ Francisco Ortin; Francisco Morero; Anton Morant (2014). "Static type information to improve the IDE features of hybrid dynamically and statically typed languages". Journal of Visual Languages & Computing. 25 (4): 346–362. doi:10.1016/j.jvlc.2014.04.002.
  8. ↑ Francisco Ortin; Daniel Zapico; J.B.G. Perez-Schofield; Miguel Garcia (2010). "Including both static and dynamic typing in the same programming language". IET Software. 4 (4): 268. doi:10.1049/iet-sen.2009.0070. hdl: 10651/9769 .
  9. ↑ Francisco Ortin (2011). "Type Inference to Optimize a Hybrid Statically and Dynamically Typed Language". The Computer Journal. 54 (11): 1901–1924. doi:10.1093/comjnl/bxr067. hdl: 10651/11411 .
  10. ↑ Miguel Garcia; Francisco Ortin; Jose Quiroga (2016). "Design and implementation of an efficient hybrid dynamic and static typing language". Software: Practice and Experience. 46 (2): 199–226. doi:10.1002/spe.2291. S2CID   2065468.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.