Subset Of Pascal Research Articles

Design of a compiler construction project

This is a description of a compiler project: a compiler for Mini-P, a substantial subset of Pascal. My goal was that the students implement a compiler that generates code executable under the Linux...

A slicing-based approach for locating type errors

The effectiveness of a type-checking tool strongly depends on the accuracy of the positional information that is associated with type errors. We present an approach where the location associated with an error message e is defined as a slice P e of the program P being type-checked. We show that this approach yields highly accurate positional information: P e is a program that contains precisely those program constructs in P that caused error e . Semantically, we have the interesting property that type-checking P e is guaranteed to produce the same error e . Our approach is completely language-independent and has been implemented for a significant subset of Pascal. We also report on experiments with object-oriented type systems, and with a subset of ML.

Testing student-made compilers

This article presents a few guidelines and examples for testing Pascal compilers designed by students in introductory courses. A standard Pascal subset with little alteration is used, and the possible sources of errors are divided into eight categories. Examples and probable sources of error are exposed for each category.

Using assertions in declarative and operational models for automated debugging

This article presents an improved method for semiautomatic bug localization, by extending our previous generalized algorithm debugging technique, (GADT) [Fritzson et al. 1991], which uses declarative assertions about program units such as procedures and operational assertions about program behavior. For example, functional properties are best expressed through declarative assertions about procedure units, whereas order-dependent properties, or sequencing constraints in general, are more easily expressed using operational semantics. A powerful assertion language, called FORMAN, has been developed to this end. Such assertions can be collected into assertion libraries, which can greatly increase the degree of automation in bug localization. The long-range goal of this work is a semiautomatic debugging and testing system, which can be used during large-scale program development of nontrivial programs. To our knowledge, the extended GADT (EGADT) presented here is the first method that uses powerful operational assertions integrated with algorithmic debugging. In addition to providing support for local-level bug localization within procedures (which is not handled well by basic algorithmic debugging), the operational assertions reduce the number of irrelevant questions to the programmer during bug localization, thus further improving bug localization. A prototype of the GADT, implemented in PASCAL, supports debugging in a subset of Pascal. An interpreter of FORMAN assertions has also been implemented in PASCAL. During bug localization, both declarative and operational assertions are evaluated on execution traces.

Generalized algorithmic debugging and testing

This paper presents a method for semi-automatic bug localization, generalized algorithmic debugging, which has been integrated with the category partition method for functional testing. In this way the efficiency of the algorithmic debugging method for bug localization can be improved by using test specifications and test results. The long-range goal of this work is a semi-automatic debugging and testing system which can be used during large-scale program development of nontrivial programs. The method is generally applicable to procedural langua ges and is not dependent on any ad hoc assumptions regarding the subject program. The original form of algorithmic debugging, introduced by Shapiro, was however limited to small Prolog programs without side-effects, but has later been generalized to concurrent logic programming languages. Another drawback of the original method is the large number of interactions with the user during bug localization. To our knowledge, this is the first method which uses category partition testing to improve the bug localization properties of algorithmic debugging. The method can avoid irrelevant questions to the programmer by categorizing input parameters and then match these against test cases in the test database. Additionally, we use program slicing, a data flow analysis technique, to dynamically compute which parts of the program are relevant for the search, thus further improving bug localization. We believe that this is the first generalization of algorithmic debugging for programs with side-effects written in imperative languages such as Pascal. These improvements together makes it more feasible to debug larger programs. However, additional improvements are needed to make it handle pointer-related side-effects and concurrent Pascal programs. A prototype generalized algorithmic debugger for a Pascal subset without pointer side-effects and a test case generator for application programs in Pascal, C, dBase, and LOTUS have been implemented.

A theory of organization

The theory of organization deals with the representation and treatment of processing Structures and their realization. It offers an algebra, which in particular is qualified for a unified description of soft- and hardware. The term replacement rules coming along with the algebra allow to change a processing structure in a variety of ways. In particular, there are order changing rules allowing to generate any representation between the minimum order of dataflow and the maximum order of a sequence. Moreover, conversion rules can be specified for the transformation of conventional programming languages into the (language of the) algebra. The same is possible for the conversion of Boolean algebra. Finally, a circuit description language can be derived from the algebra, which seems to be well suited for VLSI-layout. Part 1 of this paper covers a general introduction to the subject and the notions, the relations, and the algebra on which the theory of organization is based. Part 2 deals with nondeterminism and communicating processes, presents the conversion rules for a subset of Pascal and for Boolean expressions and introduces the circuit description language.

A theory of organization

The theory of organization deals with the representation and treatment of processing structures and their realization. It offers an algebra, which in particular is qualified for a unified description of soft- and hardware. The term replacement rules coming along with the algebra allow to change a processing structure in a variety of ways. In particular, there are order changing rules allowing to generate any representation between the minimum order of dataflow and the maximum order of a sequence. Moreover, conversion rules can be specified for the transformation of conventional programming languages into the (language of the) algebra. The same is possible for the conversion of Boolean algebra. Finally, a circuit description language can be derived from the algebra, which seems to be well suited for VLSI-layout. Part 1 of this paper covers a general introduction to the subject and the notions, the relations, and the algebra on which the theory of organization is based. Part 2 deals with nondeterminism and communicating processes, presents the conversion rules for a subset of Pascal and for Boolean expressions and introduces the circuit description language.

Incremental recursive descent parsing

The Recursive Descent method of parsing is well established in practice. An Incremental Parsing algorithm using the Recursive Descent method is presented. The algorithm is applicable to LL(1) grammars. The algorithm has been implemented for a subset of Pascal.

A multiprocessor system with fast synchronization and communication

This paper presents the design of a parallel working multiprocessor module, that evolved from the development of the ASSKO system. A common memory that allows quasi simultaneous access of parallel working processors is described together with fast hardware supported synchronization and communication mechanisms. Their speed allows an efficient parallel computation on instruction level as well as on expression level. A high level language construct for explicit description of parallelism has been added to a PASCAL subset. This enables a simple but efficient programming of the presented multiprocessor module.

An applicable family of data flow testing criteria

The authors extend the definitions of the previously introduced family of data flow testing criteria to apply to programs written in a large subset of Pascal. They then define a family of adequacy criteria called feasible data flow testing criteria, which are derived from the data-flow testing criteria. The feasible data flow testing criteria circumvent the problem of nonapplicability of the data flow testing criteria by requiring the test data to exercise only those definition-use associations which are executable. It is shown that there are significant differences between the relationships among the data flow testing criteria and the relationships among the feasible data flow testing criteria. The authors discuss a generalized notion of the executability of a path through a program unit. A script of a testing session using their data flow testing tool, ASSET, is included. >

Code Scheduling Methods for some architectural features in pipe

pipe is a very-high-performance computer architecture intended for heavily pipelined vlsi implementation. A number of architectural queues are included in the pipe architecture to reduce the influence of delay due to accessing memory. The prepare-to-branch instruction is a mechanism to decrease the penalty incurred by conditional branches. We have developed a compiler for a subset of Pascal. A code scheduler is used to reorder the compiled code to take advantage of the architectural queues and the prepare-to-branch instruction. For wellstructured code (loops), software pipelining is a technique that can take advantage further of the aforementioned features. We present the scheduling methods for automatic code scheduling and software pipelining, which can be applied to most register-register pipelined architectures by simply changing the cost table. We show the functions of these scheduling methods by examples and we illustrate some simulation results.

Automatic Compiler Production: The Front End

This paper describes a system for automatically producing complete compiler front ends from simple, nonprocedural specifications of the source language. This system is based on a detailed model of a compiler front end that is presented first. The system itself is then described using a Pascal subset as an example. This work was part of a larger project aimed at producing complete compilers in a similar fashion.

Unisex: A unix‐based symbolic executor for pascal

AbstractUNISEX is a UNIX‐based symbolic executor for Pascal. The UNISEX system provides an environment for both testing and formally verifying Pascal programs. The system supports a large subset of Pascal, runs on UNIX and provides the user with a variety of debugging features to help in the difficult task of program validation. This paper contains a brief introduction to symbolic execution, followed by an overview of the features of UNISEX, a discussion of the UNISEX Pascal language, and some of the implementation details for the UNISEX system. Finally, some of the problems encountered when designing and implementing the system are discussed as well as future directions.

Pascal circuit compiler for UK5000

A Pascal compiler is described which can parse a limited subset of Pascal, and generates a circuit description in a format which can then be input to the UK5000 gate array software. A set of Pascal utilities completes this package by allowing the Pascal circuit description to be compiled by a standard Pascal system. This complete package allows the development of systems containing single or multiple UK5000 chips. More-over this can be performed on any software development system. The use of Pascal as a hardware description language is not new, but this system promotes good top-down hierarchical design of UK5000 chips and also allows quick and efficient verification of the system, prior to the automatic generation of data for entry into the UK5000 system.

Pascal circuit compiler for UK5000

A Pascal compiler is described which can parse a limited subset of Pascal, and generates a circuit description in a format which can then be input to the UK5000 gate array software. A set of Pascal utilities completes this package by allowing the Pascal circuit description to be compiled by a standard Pascal system. This complete package allows the development of systems containing single or multiple UK5000 chips. More-over this can be performed on any software development system. The use of Pascal as a hardware description language is not new, but this system promotes good top-down hierarchical design of UK5000 chips and also allows quick and efficient verification of the system, prior to the automatic generation of data for entry into the UK5000 system.

Pascal Semantics by a Combination of Denotational Semantics and High-level Petri nets

This paper describes the formal semantics of a subset of PASCAL by means of a semantic model based on a combination of denotational semantics and high-level Petri nets. It is our intention that the paper be used as part of the written material for an introductory course in Computer Science.

DIN-A-MIT: An adaptable, distributed computer-based message system

A distributed computer-based message system in a heterogenous local computer network is introduced. DIN-A-MIT — a system of the basic modules User-Agent, Post-Station, User-Record-Base and Message-Base — can be used for varied purposes such as a Mail, a (network-) Status and a Library service. So-called “user-records” which “float” in the system due to the mobility of the user contain the link information for messages stored on different computers. One-to-one and one-to-many messages are possible by assigning attributes which represent either a unique user-name or an interest group. In all cases only a single message copy is stored. Implementation takes place in a portable subset of PASCAL based on a standardized FORTRAN interface to the network.

A sentence generator for a compiler for PT, a pascal subset

AbstractAn implementation of a sentence generator system for a compiler for PT, a subset of Pascal, is discussed. Using the syntax definition of PT, the system automatically produces leftmost generations in a pseudorandom fashion. Syntactically correct as well as compile‐time correct programs can be generated. In the generation of compile‐time correct programs, only those statements that satisfy the contextual constraints imposed by the declarative part of the generated program are generated. The system also provides the facility of producing programs that have lexical or syntactic errors. All the generated programs are printed with appropriate indentations to show structural properties. Furthermore, the number of procedures in the generated program, the number of statements, identifier length and the number of generations can be controlled. The implementation has been successfully used for testing an error recovery parser as well as an intermediate code generator for PT.

Practice and experience with BASIS: An interactive programming system for introductory courses in informatics

AbstractThe BASIS system is an interactive and conversational system, written in Pascal, to be used in the workshop of the introductory course in informatics. Its language is a subset of Pascal. Based on some years of experience with several versions of the system, we will discuss some implementational aspects.

Pascal in LCF: Semantics and examples of proof

An axiomatization in LCF of a substantial subset of PASCAL (including I O ) is presented. The syntax of such a subset is introduced and the LCF axioms defining the corresponding semantics are discussed. Sample theorems about the semantic definitions are shown. As an example of use of this axiomatization for proving properties of programs (with a machine checked proof), we present the correctness of a program for the “McCarthy Airline” reservation system. An interesting aspect of such a program is that it deals with a potentially infinite sequence of inputs. An LCF theorem asserting its (partial) correctness is then presented, with its proof, carried out using the Stanford LCF proof checker.