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(De-) Composition

Components can be decomposed to structure a system, separate concerns, and reduce complexity by distributing system functionality across multiple smaller components.

In MontiArc, component types define the decomposition of components in terms of subcomponents and connectors between the components' interfaces.

Subcomponent Declaration

Subcomponents are declared in the body of a component type, specifying the subcomponents' types and stating their names. A simple subcomponent declaration looks like 

TYPE SUB;

where

  • TYPE is the subcomponent's (qualified) type (reference)

  • SUB is the subcomponent's unique name (defining)

Subcomponents are directly instantiated alongside their declaration.

A component can have multiple subcomponents of different types but also multiple subcomponents of the same type. For convenience, multiple subcomponents of the same type can be instantiated by stating their names in a comma-separated list after the component's type, which looks like 

TYPE SUB1, SUB2;

and is a shorthand notation for 

TYPE SUB1;
TYPE SUB2;

Arguments

The instantiation of a component may require arguments, which configure the component's initial state or behavior. The component's type declaration defines the number, order, and type of arguments required. See parameters for more information.

Arguments must be provided during component instantiation and are listed after the subcomponents' name in round brackets (( )). A subcomponent declaration with arguments looks like

TYPE SUB(ARGS);

where ARGS is a comma-separated list of arguments of the form ARG1, ARG2, ...., ARGn where ARG1, ARG2, and so forth until ARGn are the first, second, and so forth until the n-th argument. All arguments are defined using expressions.

Type Arguments

Generic components require type arguments that replace the generic's type parameters with the actual types. The component's type declaration defines the number of type arguments needed, their order, and potential typing restrictions. See Generics for more information. The signature of a generic component depends in part on the provided type arguments; that is, type arguments may define the actual typing of ports and parameters.

Type arguments must be provided with the subcomponent declaration alongside the component type in angle brackets (< >).

TYPE<TARGS> SUB;

where TARGS is a comma-separated list of arguments of the form TARG1, TARG2, ...., TARGn where TARG1, TARG2, and so forth until TARGn are the first, second, and so forth until the n-th type argument.

For example, 

Delay<int> delay;

declares and instantiates a subcomponent delay of type Delay with type argument int.

Warning

Note that only data types may be used as type arguments. Component types cannot be used as type arguments.