The mCRL2 tool set [GKM+08] is a tool set for verification and validation of concurrent processes, based on process algebra speci??cations. The mCRL2 language is based on the Algebra of Communicating Processes (ACP), which is extended to include data and time. This paper reports on experiences with generic programming in C++ as applied in the implementation of the tool set. C++ concepts, a type system for templates [RS06], form a key ingredient of this style of programming. Using concept definitions, requirements on template types can be defined that are type checked during compile time. The main benefits for the mCRL2 tool set are uniform and exible interfaces that operate on well-defined types, and a signi??cant increase in code reuse. The use of concepts also promotes the writing of code that corresponds closely to pseudo code, since the chosen concepts correspond naturally with domain specific concepts. This will be illustrated by a simple use case, namely substitution functions. Generic programming is about generalizing software components, to enable reuse in a wide variety of situations. In C++, generic programming is enabled using templates. C++ concepts are proposed as a means to type check template types. A concept is a set of requirements (valid expressions, associated types, semantic invariants, complexity guarantees, and so on) that a type must fulfill to be correctly used as an argument in a call to a generic algorithm, see [RS06]. Language support for concepts has been proposed [GJS+06] for the next version of the C++ standard, C++0x. Concepts will be used to make the specification of the C++ standard library more complete and precise. A derivative of the GNU C++ compiler [Gre08] already implements language support for concepts. In the mCRL2 tool set we have used a portable library for concept checking. Most uses of generic programming in general, and more specifically the use of concepts, that are described in the literature treat the construction of data structures and algorithms that operate on these, see e.g. [GL05]

Keiren, J.J.A.

Wesselink, J.W.

Wulp, van der, J.

English

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 Generic programming in the mCRL2 toolsetCitation for published version (APA):Wesselink, J. W., Wulp, van der, J., & Keiren, J. J. A. (2010). Generic programming in the mCRL2 toolset. In F.Gervais, & B. Fraikin (Eds.), Informal Proceedings of the 1st Workshop on Tool Building in Formal Methods(TBFM'10, Orford, Québec, Canada, February 22, 2010; in conjunction with ABZ 2010) (pp. 1-3)Document status and date:Published: 01/01/2010Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 16. Nov. 2023Generic programming in the mCRL2 tool setWieger Wesselink, Jeroen van der Wulp and Jeroen KeirenTechnische Universiteit EindhovenDepartment of Mathematics and Computer ScienceP.O. Box 513, 5600 MB Eindhoven, The Netherlands{j.w.wesselink, j.j.a.keiren}@tue.nl, jeroen.vanderwulp@gmail.com1 IntroductionThe mCRL2 tool set [GKM+08] is a tool set for verification and validationof concurrent processes, based on process algebra specifications. The mCRL2language is based on the Algebra of Communicating Processes (ACP), whichis extended to include data and time. This paper reports on experiences withgeneric programming in C++ as applied in the implementation of the tool set.C++ concepts, a type system for templates [RS06], form a key ingredient of thisstyle of programming. Using concept definitions, requirements on template typescan be defined that are type checked during compile time. The main benefits forthe mCRL2 tool set are uniform and flexible interfaces that operate on well-defined types, and a significant increase in code reuse. The use of concepts alsopromotes the writing of code that corresponds closely to pseudo code, since thechosen concepts correspond naturally with domain specific concepts. This willbe illustrated by a simple use case, namely substitution functions.Generic programming is about generalizing software components, to enablereuse in a wide variety of situations. In C++, generic programming is enabledusing templates. C++ concepts are proposed as a means to type check templatetypes. A concept is a set of requirements (valid expressions, associated types,semantic invariants, complexity guarantees, and so on) that a type must fulfillto be correctly used as an argument in a call to a generic algorithm, see [RS06].Language support for concepts has been proposed [GJS+06] for the next versionof the C++ standard, C++0x. Concepts will be used to make the specificationof the C++ standard library more complete and precise. A derivative of theGNU C++ compiler [Gre08] already implements language support for concepts.In the mCRL2 tool set we have used a portable library for concept checking.Most uses of generic programming in general, and more specifically the useof concepts, that are described in the literature treat the construction of datastructures and algorithms that operate on these, see e.g. [GL05].2 The mCRL2 tool setThe mCRL2 tool set stores data structures like state spaces and parameterizedboolean equation systems using terms. A frequent operation in algorithms on2these data structures is substitution on terms. A substitution concept has beendefined, and applied throughout the tool set, together with a traversal frameworkfor data structures. This has made quite a number of existing replace functionson terms obsolete, and many more ad hoc solutions for less general substitutionproblems as well. The introduction of the substitution concept has also openedthe way to easily experiment with different implementations of substitution func-tions, instead of with a fixed number of predefined ones. C++ concepts have beenapplied at several other places. We have, for example, defined a rewriter conceptthat has helped to make the term rewriter fully replaceable.3 ExampleBy means of example we take the substitution concept that has been defined inthe tool set. A substitution is a function that maps variables from a domain V toterms of a range T. Let x be a variable, t a term, and σ : V→ T a substitutionthat models a Substitution concept, that has the following requirements:– Substitution::variable type is a valid C++ type– Substitution::term type is a valid C++ type– σ(x) is a valid expression of type Substitution::term type– σ[x] = t is a valid C++ expressionThe first three requirements correspond to the ordinary mathematical func-tion concept. We have used the domain specific names variable type andterm type instead of the usual names argument type and result type. Thethird requirement defines the syntax for function application and expresses thatthe function call operator must be overloaded. The last requirement applies tomutable substitutions, and defines the syntax for updating a substitution. Thesemantics of the statement σ[x] = t is that σ := σ[x→ t], where σ[x→ t](y) = tif y = x and σ[x→ t](y) = σ(y) otherwise.An algorithm that takes an argument σ that models the Substitution con-cept, can only rely on the four requirements that are given here. Using a tech-nique called concept checking one can detect at compile time if an argumenttype satisfies all these requirements. Moreover, one can easily test if an algo-rithm does not inadvertently use other properties of a type. As an example weconsider the implementation of a function f that applies the substitution x := tto a process p:void f(process &p, variable x, term t) {substitution sigma; // use a predefined map based substitution classsigma[x] = t; // add the substitution x -> t to sigmasubstitute(p, sigma); // apply sigma globally to terms in p}Here substitute is a generic function with the following interface:template <typename Object, typename Substitution>void rewrite(Object& o, Substitution sigma);3It applies σ to an object o that may be one of the mCRL2 data structurescontaining terms. Overloads have been added for C++ standard containers andmCRL2 specific containers containing elements of these data structures. To im-plement the substitute function a reusable traversal framework for hierarchicalmCRL2 data structures has been defined.4 DiscussionThe substitution concept that was discussed in the previous section may lookdeceptively simple. Applying this concept globally however has lead to a remark-able cleanup of the code. At many places interfaces have become simpler andat the same time more generic. Virtually all of the more complicated and lessgeneric solutions for substitutions could be removed. An interesting and chal-lenging application was the definition of a term rewriter concept. Applying thisconcept globally took a significant effort, caused by problems in the existing in-terface. The result of this operation is that many algorithms in the mCRL2 toolset that require a rewriter for their computations have been parameterized witha Rewriter template argument. This has significant advantages. First of all itopens the possibility to experiment with different implementations of a rewriterwithout having to modify the code of these algorithms. This is useful for instancefor doing benchmarks. Another advantage of using concepts in the interfaces ofalgorithms is the explicit documentation of type requirements. Having clear se-mantics of types is a necessary step towards making correct implementations.Finally, the usage of concepts promotes the writing of clean code that corre-sponds almost one to one to pseudo code descriptions of algorithms. For manyalgorithms in the mCRL2 tool set descriptions in pseudo code are available.Concluding we can say that the application of generic programming tech-niques in the mCRL2 tool set attributes to increased productivity through uni-form and flexible interfaces, and to decreased maintenance costs through anincreased level of reuse of code written at a higher level of abstraction.References[GJS+06] D. Gregor, J. Järvi, J. Siek, B. Stroustrup, G. Dos Reis, and A. Lumsdaine.Concepts: Linguistic support for generic programming in C++. In Proc.OOPSLA’06, pages 291–310. ACM Press, October 2006.[GKM+08] J.F. Groote, J. Keiren, A. Mathijssen, B. Ploeger, F. Stappers, C. Tankink,Y. Usenko, M. van Weerdenburg, W. Wesselink, T. Willemse, and J. van derWulp. The mCRL2 toolset. In Proc. WASDeTT’08), 2008.[GL05] R. Garcia and A. Lumsdaine. MultiArray: a C++ library for generic pro-gramming with arrays. Softw., Pract. Exper., 35(2):159–188, 2005.[Gre08] D. Gregor. ConceptGCC — a prototype compiler for cpp con-cepts. http://www.generic-programming.org/software/ConceptGCC/,January 2008.[RS06] G. Dos Reis and B. Stroustrup. Specifying c++ concepts. In Proc.POPL’06, pages 295–308, New York, NY, USA, 2006. ACM.

Generic programming in the mCRL2 toolset

 Generic programming in the mCRL2 toolsetCitation for published version (APA):Wesselink, J. W., Wulp, van der, J., & Keiren, J. J. A. (2010). Generic programming in the mCRL2 toolset. In F.Gervais, & B. Fraikin (Eds.), Informal Proceedings of the 1st Workshop on Tool Building in Formal Methods(TBFM'10, Orford, Québec, Canada, February 22, 2010; in conjunction with ABZ 2010) (pp. 1-3)Document status and date:Published: 01/01/2010Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 08. Jul. 2024Generic programming in the mCRL2 tool setWieger Wesselink, Jeroen van der Wulp and Jeroen KeirenTechnische Universiteit EindhovenDepartment of Mathematics and Computer ScienceP.O. Box 513, 5600 MB Eindhoven, The Netherlands{j.w.wesselink, j.j.a.keiren}@tue.nl, jeroen.vanderwulp@gmail.com1 IntroductionThe mCRL2 tool set [GKM+08] is a tool set for verification and validationof concurrent processes, based on process algebra specifications. The mCRL2language is based on the Algebra of Communicating Processes (ACP), whichis extended to include data and time. This paper reports on experiences withgeneric programming in C++ as applied in the implementation of the tool set.C++ concepts, a type system for templates [RS06], form a key ingredient of thisstyle of programming. Using concept definitions, requirements on template typescan be defined that are type checked during compile time. The main benefits forthe mCRL2 tool set are uniform and flexible interfaces that operate on well-defined types, and a significant increase in code reuse. The use of concepts alsopromotes the writing of code that corresponds closely to pseudo code, since thechosen concepts correspond naturally with domain specific concepts. This willbe illustrated by a simple use case, namely substitution functions.Generic programming is about generalizing software components, to enablereuse in a wide variety of situations. In C++, generic programming is enabledusing templates. C++ concepts are proposed as a means to type check templatetypes. A concept is a set of requirements (valid expressions, associated types,semantic invariants, complexity guarantees, and so on) that a type must fulfillto be correctly used as an argument in a call to a generic algorithm, see [RS06].Language support for concepts has been proposed [GJS+06] for the next versionof the C++ standard, C++0x. Concepts will be used to make the specificationof the C++ standard library more complete and precise. A derivative of theGNU C++ compiler [Gre08] already implements language support for concepts.In the mCRL2 tool set we have used a portable library for concept checking.Most uses of generic programming in general, and more specifically the useof concepts, that are described in the literature treat the construction of datastructures and algorithms that operate on these, see e.g. [GL05].2 The mCRL2 tool setThe mCRL2 tool set stores data structures like state spaces and parameterizedboolean equation systems using terms. A frequent operation in algorithms on2these data structures is substitution on terms. A substitution concept has beendefined, and applied throughout the tool set, together with a traversal frameworkfor data structures. This has made quite a number of existing replace functionson terms obsolete, and many more ad hoc solutions for less general substitutionproblems as well. The introduction of the substitution concept has also openedthe way to easily experiment with different implementations of substitution func-tions, instead of with a fixed number of predefined ones. C++ concepts have beenapplied at several other places. We have, for example, defined a rewriter conceptthat has helped to make the term rewriter fully replaceable.3 ExampleBy means of example we take the substitution concept that has been defined inthe tool set. A substitution is a function that maps variables from a domain V toterms of a range T. Let x be a variable, t a term, and σ : V→ T a substitutionthat models a Substitution concept, that has the following requirements:– Substitution::variable type is a valid C++ type– Substitution::term type is a valid C++ type– σ(x) is a valid expression of type Substitution::term type– σ[x] = t is a valid C++ expressionThe first three requirements correspond to the ordinary mathematical func-tion concept. We have used the domain specific names variable type andterm type instead of the usual names argument type and result type. Thethird requirement defines the syntax for function application and expresses thatthe function call operator must be overloaded. The last requirement applies tomutable substitutions, and defines the syntax for updating a substitution. Thesemantics of the statement σ[x] = t is that σ := σ[x→ t], where σ[x→ t](y) = tif y = x and σ[x→ t](y) = σ(y) otherwise.An algorithm that takes an argument σ that models the Substitution con-cept, can only rely on the four requirements that are given here. Using a tech-nique called concept checking one can detect at compile time if an argumenttype satisfies all these requirements. Moreover, one can easily test if an algo-rithm does not inadvertently use other properties of a type. As an example weconsider the implementation of a function f that applies the substitution x := tto a process p:void f(process &p, variable x, term t) {substitution sigma; // use a predefined map based substitution classsigma[x] = t; // add the substitution x -> t to sigmasubstitute(p, sigma); // apply sigma globally to terms in p}Here substitute is a generic function with the following interface:template <typename Object, typename Substitution>void rewrite(Object& o, Substitution sigma);3It applies σ to an object o that may be one of the mCRL2 data structurescontaining terms. Overloads have been added for C++ standard containers andmCRL2 specific containers containing elements of these data structures. To im-plement the substitute function a reusable traversal framework for hierarchicalmCRL2 data structures has been defined.4 DiscussionThe substitution concept that was discussed in the previous section may lookdeceptively simple. Applying this concept globally however has lead to a remark-able cleanup of the code. At many places interfaces have become simpler andat the same time more generic. Virtually all of the more complicated and lessgeneric solutions for substitutions could be removed. An interesting and chal-lenging application was the definition of a term rewriter concept. Applying thisconcept globally took a significant effort, caused by problems in the existing in-terface. The result of this operation is that many algorithms in the mCRL2 toolset that require a rewriter for their computations have been parameterized witha Rewriter template argument. This has significant advantages. First of all itopens the possibility to experiment with different implementations of a rewriterwithout having to modify the code of these algorithms. This is useful for instancefor doing benchmarks. Another advantage of using concepts in the interfaces ofalgorithms is the explicit documentation of type requirements. Having clear se-mantics of types is a necessary step towards making correct implementations.Finally, the usage of concepts promotes the writing of clean code that corre-sponds almost one to one to pseudo code descriptions of algorithms. For manyalgorithms in the mCRL2 tool set descriptions in pseudo code are available.Concluding we can say that the application of generic programming tech-niques in the mCRL2 tool set attributes to increased productivity through uni-form and flexible interfaces, and to decreased maintenance costs through anincreased level of reuse of code written at a higher level of abstraction.References[GJS+06] D. Gregor, J. Järvi, J. Siek, B. Stroustrup, G. Dos Reis, and A. Lumsdaine.Concepts: Linguistic support for generic programming in C++. In Proc.OOPSLA’06, pages 291–310. ACM Press, October 2006.[GKM+08] J.F. Groote, J. Keiren, A. Mathijssen, B. Ploeger, F. Stappers, C. Tankink,Y. Usenko, M. van Weerdenburg, W. Wesselink, T. Willemse, and J. van derWulp. The mCRL2 toolset. In Proc. WASDeTT’08), 2008.[GL05] R. Garcia and A. Lumsdaine. MultiArray: a C++ library for generic pro-gramming with arrays. Softw., Pract. Exper., 35(2):159–188, 2005.[Gre08] D. Gregor. ConceptGCC — a prototype compiler for cpp con-cepts. http://www.generic-programming.org/software/ConceptGCC/,January 2008.[RS06] G. Dos Reis and B. Stroustrup. Specifying c++ concepts. In Proc.POPL’06, pages 295–308, New York, NY, USA, 2006. ACM.

The mCRL2 tool set [GKM+08] is a tool set for verification and validation of concurrent processes, based on process algebra speci??cations. The mCRL2 language is based on the Algebra of Communicating Processes (ACP), which is extended to include data and time. This paper reports on experiences with generic programming in C++ as applied in the implementation of the tool set. C++ concepts, a type system for templates [RS06], form a key ingredient of this style of programming. Using concept definitions, requirements on template types can be defined that are type checked during compile time. The main benefits for the mCRL2 tool set are uniform and 
exible interfaces that operate on well-defined types, and a signi??cant increase in code reuse. The use of concepts also promotes the writing of code that corresponds closely to pseudo code, since the chosen concepts correspond naturally with domain specific concepts. This will be illustrated by a simple use case, namely substitution functions.
Generic programming is about generalizing software components, to enable reuse in a wide variety of situations. In C++, generic programming is enabled using templates. C++ concepts are proposed as a means to type check template types. A concept is a set of requirements (valid expressions, associated types, semantic invariants, complexity guarantees, and so on) that a type must fulfill to be correctly used as an argument in a call to a generic algorithm, see [RS06]. Language support for concepts has been proposed [GJS+06] for the next version of the C++ standard, C++0x. Concepts will be used to make the specification of the C++ standard library more complete and precise. A derivative of the GNU C++ compiler [Gre08] already implements language support for concepts. In the mCRL2 tool set we have used a portable library for concept checking.
Most uses of generic programming in general, and more specifically the use of concepts, that are described in the literature treat the construction of data structures and algorithms that operate on these, see e.g. [GL05]

Generic programming in the mCRL2 toolset

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