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MontiCore - Types

Type systems are available in a variety of (programming) languages and facilitate programming because they allow for detecting typing errors already at compile time. To express type usages in MontiCore-based languages a language component hierarchy for type modeling was developed. The hierarchy consists of the following language components:

MCBasicTypes

MCBasicTypes is the most basic language component. It provides the central interface nonterminal MCType. Additionally, it defines nonterminals that enable modeling primitive types as well as qualified and non-qualified types. Furthermore, the component comprises a rule that covers return types which can be MCTypes or voids. In general, the component represents a relativity small, yet useful, collection of rules for type modeling that supports statements such as int, Person, and java.lang.String.

MCCollectionTypes

This language component builds upon MCBasicTypes and enables to model four kinds of generics:

  • Set
  • List
  • Map
  • Optional

These generics cannot be nested as the purpose of the MCCollectionTypes language component is the provisioning of some commonly used collection types whose functionality is limited to support the construction of high-level models. With the language component types such as List<Integer>, Set<char>, or Map<java.lang.String, Person> become expressible.

MCSimpleGenericTypes

This language component extends the MCCollectionTypes component to allow the expression of types with custom generics of arbitrary classes with arbitrary arguments. When using the component, types such as Person<String> or Map<Person<String>, Integer> are expressible. Please note that these types still do not cover all possible Java types as Java additionally supports inner types of generic types. Specifically, types such as a.b.C<D>.E.F<G>.H are not expressible by MCSimpleGenericTypes.

MCFullGenericTypes

This language component extends the MCSimpleGenericTypes component to allow the expression of inner generic types of arbitrary classes with arbitrary arguments including wild card types. When using this language component, types such as Person<?>, Map<Person<String>, ? extends Person>, and a.b.C<D>.E.F<G>.H are expressible.

TypeParameters

This language component offers ways to define type parameter lists for generic model elements, e.g., generic classes such as Map<K, V>. The resulting Symbols can than be used with, e.g., MCSimpleGenericTypes, or MCFullGenericTypes to define types by providing the corresponding type arguments. Type parameters may optionally have upper bounds, e.g., T extends Person, U extends T & Comparable<U>.

MCArrayTypes

This language component allows to express array types like Person[] or int[][]. As array types are orthogonal to other kinds of types, MCArrayTypes can be combined with any of the above language components.

MCFunctionTypes

This language component allows developers to express function types like int -> int or (String -> int) -> void. Function types are independent from and not interfering with generic and array types, MCFunctionTypes can be combined with any of the above language components.

MCStructuralTypes

This language component allows to express additional types by combining other types, like the union type Foo | Bar which is the type that is "Foo or Bar". As structural types are orthogonal to other kinds of types, MCStructuralTypes can be combined with any of the above language components.

SIUnitTypes4Math

When using this language component, SI unit types like [km/h] become expressible. The documentation can be found in SIUnits.

SIUnitTypes4Computing

When using this language component, SI unit types like [km/h]<int> become expressible. The documentation can be found in SIUnits.

RegExType

When using this language component, Subtypes of String defined as RegEx types like R"H(a|e)llo", or R"-?[0-9]+" R"0x[a-f0-9]+" become expressible. This is useful to prevent e.g. security breaches by malign input text. This is documented in RegEx.

Further Information