Formal Semantics as a Language Designer's Toolbox Paolo G. - - PowerPoint PPT Presentation
Formal Semantics as a Language Designer's Toolbox Paolo G. Giarrusso Klaus Ostermann Tillmann Rendel University of Marburg University of Tbingen Eric Walkingshaw University of Marburg Oregon State University Presentation by
Formal Semantics
as a Language Designer's
Toolbox
Paolo G. Giarrusso · Klaus Ostermann · Tillmann Rendel University of Marburg · University of Tübingen Eric Walkingshaw University of Marburg · Oregon State University
Presentation by Tillmann Rendel at the Second International Workshop
in Portland, Oregon, October 20, 2014
The great work
easier and easier
so more and more
programmers
build their own custom
and become
and
at the same time
is still
How can a
programmer/ language designer
learn to design languages that are
Formal Semantics
(it's their job)
(they are mathematicians)
Elegant = powerful and simple, less to learn
Can formal semantics guide a programmer/language designer towards an elegant and usable design?
Problem 1
semantics, just let the insights of formal semantics guide your design process.
Problem 2
understandable to the working programmer/language designers
formal semantics as language design patterns.
Language Design Patterns
we want to adapt them for language design
programmer/language designer
elegant, usable languages.
Bound & Binding Occurrences How to structure names? Distinguish bound and binding
You can reason about the naming structure of a program in terms of „this name here is bound there“ name problem solution effects
Bound & Binding Occurrences How to structure names? Distinguish bound and binding
You can reason about the naming structure of a program in terms of „this name here is bound there“ name problem solution effects Lexical Scoping Which bound occurrence refers to which binding occurrence? All bound occurrences in a continuous region of the source file bind to the same binding
You can reason about the binding structure statically. name problem solution effects
Bound & Binding Occurrences How to structure names? Distinguish bound and binding
You can reason about the naming structure of a program in terms of „this name here is bound there“ name problem solution effects Lexical Scoping Which bound occurrence refers to which binding occurrence? All bound occurrences in a continuous region of the source file bind to the same binding
You can reason about the binding structure statically. name problem solution effects Domain-Specific Scoping Which bound occurrence refers to which binding occurrence? Use domain-specific criteria to match bound to binding
Your binding structure supports your domain integration. name problem solution effects
Meaning How to specify the semantics? Map every program to its meaning. Allows to identify programs that mean the same but work differently internally. name problem solution effects
Meaning How to specify the semantics? Map every program to its meaning. Allows to identify programs that mean the same but work differently internally. name problem solution effects Simple Meaning How to structure the meaning? Choose the simplest thing that works. Carefully choosing the meaning helps you focus your design on your domain. name problem solution effects
Meaning How to specify the semantics? Map every program to its meaning. Allows to identify programs that mean the same but work differently internally. name problem solution effects Simple Meaning How to structure the meaning? Choose the simplest thing that works. Carefully choosing the meaning helps you focus your design on your domain. name problem solution effects Recursive Meaning How to define the meaning mapping? Map each phrase of the program to its meaning. You can explain what a part of a program means. name problem solution effects
Meaning How to specify the semantics? Map every program to its meaning. Allows to identify programs that mean the same but work differently internally. name problem solution effects Simple Meaning How to structure the meaning? Choose the simplest thing that works. Carefully choosing the meaning helps you focus your design on your domain. name problem solution effects Recursive Meaning How to define the meaning mapping? Map each phrase of the program to its meaning. You can explain what a part of a program means. name problem solution effects Compositional Meaning How to define the meaning mapping? Define the meaning of a phrase in terms of the meaning of its subphrases. The meaning of a phrase is the phrase's interface. Allow code moving without changing meaning. name problem solution effects
Type Structure How to structure the primitives? Structure your language design around the available types of
the interfaces of the types. Easier to not forget primitives. Structuring principle also for documentation. name problem solution effects
Type Structure How to structure the primitives? Structure your language design around the available types of
the interfaces of the types. Easier to not forget primitives. Structuring principle also for documentation. name problem solution effects Constructor Which operations for a type? Provide constructors for making new values of a type. User programs can create values of the type. name problem solution effects
Type Structure How to structure the primitives? Structure your language design around the available types of
the interfaces of the types. Easier to not forget primitives. Structuring principle also for documentation. name problem solution effects Constructor Which operations for a type? Provide constructors for making new values of a type. User programs can create values of the type. name problem solution effects Destructor Which operations for a type? Provide destructors for getting information out of values of a type. User programs can use values of the type. name problem solution effects
Type Structure How to structure the primitives? Structure your language design around the available types of
the interfaces of the types. Easier to not forget primitives. Structuring principle also for documentation. name problem solution effects Constructor Which operations for a type? Provide constructors for making new values of a type. User programs can create values of the type. name problem solution effects Destructor Which operations for a type? Provide destructors for getting information out of values of a type. User programs can use values of the type. name problem solution effects Information Preservation How to balance constructors and destructors? Provide enough destructors to get all information out of an constructed value. Provide enough constructors to recreate a destructed value. No identity and no secrets. Name problem solution effects
Language Design Patterns ...
(„think of all constructors“)
(„separate constructors and destructors“)
(„which kind of scoping is appropriate?“)
interface, a simple meaning is a better interface“)
Conclusion
semantics as language design patterns
that make sense to the working programmer/language designer
Collect language design patterns and distill them into a coherent pattern language.