Catching bugs in the web of program invariants

FlanaganCormac,; FlattMatthew,; KrishnamurthiShriram,; WeirichStephanie,; FelleisenMatthias,

doi:10.1145/249069.231387

Cited by 37 publications

(34 citation statements)

References 18 publications

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“…Roughly speaking, these soft typing systems introduce sets-of-values constraints for atomic expressions and propagate them via a generalized transitive-closure propagation (Aiken et al 1994;Flanagan and Felleisen 1999). In this world, it is easy to communicate to a programmer how a values might flow into a particular operation and violate a type invariant, thus eliminating one of the major problems of Hindley-Milner based soft typing (Flanagan et al 1996).…”

Section: Types For Schemementioning

confidence: 99%

The design and implementation of typed scheme

Tobin-Hochstadt

Felleisen

2008

Proceedings of the 35th Annual ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages

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231

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When scripts in untyped languages grow into large programs, maintaining them becomes difficult. A lack of types in typical scripting languages means that programmers must (re)discover critical pieces of design information every time they wish to change a program. This analysis step both slows down the maintenance process and may even introduce mistakes due to the violation of undiscovered invariants.This paper presents Typed Scheme, an explicitly typed extension of an untyped scripting language. Its type system is based on the novel notion of occurrence typing, which we formalize and mechanically prove sound. The implementation of Typed Scheme additionally borrows elements from a range of approaches, including recursive types, true unions and subtyping, plus polymorphism combined with a modicum of local inference. Initial experiments with the implementation suggest that Typed Scheme naturally accommodates the programming style of the underlying scripting language, at least for the first few thousand lines of ported code. Categories and Subject Descriptors Type Refactoring: From Scripts to ProgramsRecently, under the heading of "scripting languages", a variety of new languages have become popular, and even pervasive, in weband systems-related fields. Due to their popularity, programmers often create scripts that then grow into large applications.Most scripting languages are untyped and have a flexible semantics that makes programs concise. Many programmers find these attributes appealing and use scripting languages for these reasons. Programmers are also beginning to notice, however, that untyped scripts are difficult to maintain over the long run. The lack of types means a loss of design information that programmers must recover every time they wish to change existing code. Both the Perl community (Tang 2007) and the JavaScript community (ECMA International 2007) are implicitly acknowledging this problem with the Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. POPL'08, January 7-12, 2008 In the meantime, industry faces the problem of porting existing application systems from untyped scripting languages to the typed world. Based on our own experience, we have proposed a theoretical model for this conversion process and have shown that partial conversions can benefit from type-safety properties to the desired extent (Tobin-Hochstadt and Felleisen 2006). The key assumption behind our work is the existence of an explicitly typed version of the scripting language, with the same semantics as the original language, so that values can freely flow back and forth between typed and untyped modules. In other words, we imagine that programmers can simply add t...

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Section: Types For Schemementioning

confidence: 99%

The design and implementation of typed scheme

Tobin-Hochstadt

Felleisen

2008

Proceedings of the 35th Annual ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages

Self Cite

231

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“…The most advanced DrScheme tool is MrSpidey, a static debugger (Bourdoncle, 1993;Flanagan et al, 1996) that uses a form of set-based analysis (Flanagan & Felleisen, 1997;Heintze, 1994) to perform type inference and to mark potential errors. The static debugger tool infers constraints on the flow of values in a Scheme program.…”

Section: Static Debuggingmentioning

confidence: 99%

DrScheme: a programming environment for Scheme

et al. 2002

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DrScheme is a programming environment for Scheme. It fully integrates a graphicsenriched editor, a parser for multiple variants of Scheme, a functional read-eval-print loop, and an algebraic printer. The environment is especially useful for students, because it has a tower of syntactically restricted variants of Scheme that are designed to catch typical student mistakes and explain them in terms the students understand. The environment is also useful for professional programmers, due to its sophisticated programming tools, such as the static debugger, and its advanced language features, such as units and mixins.Beyond the ordinary programming environment tools, DrScheme provides an algebraic stepper, a context-sensitive syntax checker, and a static debugger. The stepper reduces Scheme programs to values, according to the reduction semantics of Scheme. It is useful for explaining the semantics of linguistic facilities and for studying the behavior of small programs. The syntax checker annotates programs with font and color changes based on the syntactic structure of the program. On demand, it draws arrows that point from bound to binding occurrences of identifiers. It also supports α-renaming. Finally, the static debugger provides a type inference system that explains specific inferences in terms of a value-flow graph, selectively overlaid on the program text.

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“…al [8] presented a tool for static debugging of Scheme programs. The system uses set-based analysis [15,9] to identify potential run-time errors.…”

Section: Related Workmentioning

confidence: 99%

A soft-typing system for Erlang

Nyström

2003

Proceedings of the 2003 ACM SIGPLAN Workshop on Erlang

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This paper presents a soft-typing system for the programming language Erlang. The system is based on two concepts; a (forward) data flow analysis that determines upper approximations of the possible values of expressions and other constructs, and a specification language that allows the programmer to specify the interface of a module. We examine the programming language Erlang and point to various aspects of the language that make it hard to type. We present experimental result of applying the soft-typing system to some previously written programs.

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Catching bugs in the web of program invariants

Cited by 37 publications

References 18 publications

The design and implementation of typed scheme

The design and implementation of typed scheme

DrScheme: a programming environment for Scheme

A soft-typing system for Erlang

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