Practical Foundations for Programming Languages

Types are the central organizing principle of the theory of programming languages. In this innovative book, Professor Robert Harper offers a fresh perspective on the fundamentals of these languages through the use of type theory. Whereas most textbooks on the subject emphasize taxonomy, Harper instead emphasizes genetics, examining the building blocks from which all programming languages are constructed. Language features are manifestations of type structure. The syntax of a language is governed by the constructs that define its types, and its semantics is determined by the interactions among those constructs. The soundness of a language design - the absence of ill-defined programs - follows naturally. Professor Harper's presentation is simultaneously rigorous and intuitive, relying on only elementary mathematics. The framework he outlines scales easily to a rich variety of language concepts and is directly applicable to their implementation. The result is a lucid introduction to programming theory that is both accessible and practical This Book Offers A Fresh Perspective On The Fundamentals Of Programming Languages Through The Use Of Type Theory-- Syntactic Objects Programming Languages Are Languages, A Means Of Expressing Computations In A Form Comprehensible To Both People And Machines. The Syntax Of A Language Specifies The Means By Which Various Sorts Of Phrases (expressions, Commands, Declarations, And So Forth) May Be Combined To Form Programs. But What Sort Of Thing Are These Phrases? What Is A Program Made Of? The Informal Concept Of Syntax May Be Seen To Involve Several Distinct Concepts. The Surface, Or Concrete, Syntax Is Concerned With How Phrases Are Entered And Displayed On A Computer. The Surface Syntax Is Usually Thought Of As Given By Strings Of Characters From Some Alphabet (say, Ascii Or Unicode). The Structural, Or Abstract, Syntax Is Concerned With The Struc- 4 1.1 Abstract Syntax Trees Ture Of Phrases, Specifically How They Are Composed From Other Phrases. At This Level A Phrase Is A Tree, Called An Abstract Syntax Tree, Whose Nodes Are Operators That Combine Several Phrases To Form Another Phrase. The Binding Structure Of Syntax Is Concerned With The Introduction And Use Of Identifiers: How They Are Declared, And How Declared Identifiers Are To Be Used. At This Level Phrases Are Abstract Binding Trees, Which Enrich Abstract Syntax Trees With The Concepts Of Binding And Scope. We Will Not Concern Ourselves In This Book With Matters Of Concrete Syntax, But Will Instead Work At The Level Of Abstract Syntax. To Prepare The Ground For The Rest Of The Book, We Begin In This Chapter By Definin-ing Abstract Syntax Trees And Abstract Binding Trees And Some Functions And Relations Associated With Them. The Definitions Are A Bit Technical, But Are Absolutely Fundamental To What Follows. It Is Probably Best To Skim This Chapter On First Reading, Returning To It Only As The Need Arises-- Machine Generated Contents Note: Part I. Judgments And Rules: 1. Inductive Definitions; 2. Hypothetical Judgments; 3. Syntactic Objects; 4. Generic Judgments; Part Ii. Levels Of Syntax: 5. Concrete Syntax; 6. Abstract Syntax; Part Iii. Statics And Dynamics: 7. Statics; 8. Dynamics; 9. Type Safety; 10. Evaluation Dynamics; Part Iv. Function Types: 11. Function Definitions And Values; 12. Godel's System T; 13. Plotkin's Pcf; Part V. Finite Data Types: 14. Product Types; 15. Sum Patterns; 16. Pattern Matching; 17. Generic Programming; Part Vi. Infinite Data Types: 18. Inductive And Co-inductive Types; 19. Recursive Types; Part Vii. Dynamic Types: 20. The Untyped 1-calculus; 21. Dynamic Typing; 22. Hybrid Typing; Part Viii. Variable Types: 23. Girard's System F; 24. Abstract Types; 25. Constructors And Kinds; 26. Indexed Families Of Types; Part Ix. Subtyping: 27. Subtyping; 28. Singleton And Dependent Kinds; Part X. Classes And Methods: 29. Dynamic Dispatch; 30. Inheritance; Part Xi. Control Effects: 31. Control Stacks; 32. Exceptions; 33. Continuations; Part Xii. Types And Propositions: 34. Constructive Logic; 35. Classical Logic; Part Xiii. Symbols: 36. Symbols; 37. Fluid Binding; 38. Dynamic Classification; Part Xiv. Storage Effects: 39. Modernized Algol; 40. Mutable Data Structures; Part Xv. Laziness: 41. Lazy Evaluation; 42. Polarization; Part Xvi. Parallelism: 43. Nested Parallelism; 44. Futures And Speculation; Part Xvii. Concurrency: 45. Process Calculus; 46. Current Algol; 47. Distributed Algol; Part Xviii. Modularity: 48. Separate Compilation And Linking; 49. Basic Modules; 50. Parameterized Modules; Part Xix. Equivalence: 51. Equational Reasoning For T; 52. Equational Reasoning For Pcf; 53. Parametricity. Robert Harper. Includes Bibliographical References (p. [457]-463) And Index.