Design and implementation of a reusable type inference engine and its application to Scheme

Static type checking allows programmers to locate potential bugs prior to code execution. However, developing a static type checker is a complicated endeavor. Implementers must address a number of concerns including recursion over syntax elements, unification of type variables within environments, and generation of meaningful error messages for users. The inherent complexity of type checkers can lead to code that is difficult to both understand and maintain. This thesis presents the design and implementation of an abstract type inference engine and its use in the revision of a student-oriented type checker for the Scheme programming language. Our inference engine provides a complete set of unification facilities to programmers for the specication of a type checking system. It allows for a clean separation of unification algorithms, inference rules, and error generation. We also demonstrate the applicability of the engine by using it to construct a type checker for Scheme targeted at novice programmers. This checker borrows a student-friendly type notation from a previous version and extends its system, providing for language native module support, a more complete treatment of advanced data types, and better error messages

A preliminary investigation of the effects of FORTRAN data declaration and type conversion features on program comprehension

FORTRAN permits both explicit and implicit options for both data declaration and type conversion features. This study investigated the effects of explicit and implicit data declaration and type conversion features on a program comprehension task performed by FORTRAN pro­grammers in an introductory programming course. The results indicated that both factors had significant effects on programmer performance and there was a significant interaction between data declaration and type conversion. In addition, hand-simulation tasks performed by the sub­jects provided insights on low-level errors made by the novices and misconceptions in the minds of novices

An Incremental Language Conversion Method to Convert C++ into Ada95

This thesis develops a methodology to incrementally convert a legacy object oriented C++ application into Ada95. Using the experience of converting a graphic application, called Remote Debriefing Tool (RDT), in the Graphics Lab of the Air Force Institute of Technology (AFIT), this effort defined a process to convert a C++ application into Ada95. The methodology consists of five phases: (1) reorganizing the software application, (2) breaking mutual dependencies, (3) creating package specifications to interface the existing C++ classes, (4) converting C++ code into Ada programs, and (5) embellishing. This methodology used the GNAT\u27s C++ low level interface capabilities to support the incremental conversion. The goal of this methodology is not only to correctly convert C++ code into Ada95, but also to take advantage of Ada\u27s features which support good software engineering principles

The safety of industrially-based controllers incorporating software

This thesis is concerned with the safety of industrial controllers which incorporate software. Software safety is compared with software reliability as a means of discussing the special concerns of safety. Definitions are given for the terms hazard, risk, danger and safe. A relationship between these terms has been attempted and the philosophy of safety is discussed. A formal definition of software safety is given. The factors influencing the development of software are examined. The subjectivity of safety is discussed in the context of safety measurement being a conjoint measurement. Methods of assessing the risk resulting from the use of software are described along with a discussion on the impracticability of using state transition diagrams to isolate catastrophic failure conditions. Categories of danger are discussed and three categories are advanced. The structuring of the software for safety is discussed and the principle of using safety modules and integrity locks is proposed. In discussing the reasons for errors remaining present in the software after testing two methods of measurement are suggested; Plexus and Fallibility Index. The need to declare variables is discussed. An experiment involving 119 volunteers was conducted to examine the influence of the length of variable names'on the correct usage. It was found that variables with a character length of 7 have a better probability of correct interpretation than others. The methods of assessing safety are discussed and the measurements proposed were applied to a commercially available product in the form of a Software Safety Audit. It is concluded that some aspects of the safety of controllers incorporating software can be quantified and that further research is needed

An Empirical Study on The Impact of C++ Lambdas And Programmer Experience

Lambda functions have become prevalent in mainstream programming languages, as they are increasingly introduced to widely used object oriented programming languages such as Java and C++. Some in the scientific literature argue that this feature increases programmer productivity, ease of reading, and makes parallel programming easier. Others are less convinced, citing concerns that the use of lambdas makes debugging harder. This thesis describes the design, execution and results of an experiment to test the impact of using lambda functions compared to the iterator design pattern for iteration tasks, as a first step in evaluating these claims. The approach is a randomized controlled trial, which focuses on the percentage of tasks completed, number of compiler errors, the percentage of time to fix such errors, and the amount of time it takes to complete programming tasks correctly. The overall goal is to investigate, if lambda functions have an impact on the ability of developers to complete tasks, or the amount of time taken to complete them. Additionally, it is tested if developers introduce more errors while using lambda functions and if fixing errors takes them more time. Lastly, the impact of experience level on productivity is evaluated by comparing the performance of participants from different levels of experience with one-another. Participants were assigned one of five levels based on their progress in the computer science major. The five levels were freshman, sophomore, junior, senior and professional. The professional level was assigned to individuals out of school with 5 or more years of professional experience. Results show that the impact of using lambdas, as opposed to iterators, on the number of tasks completed was significant. The impact on time to completion, number of errors introduced during the experiment and times spent fixing errors were also found to be significant. The analysis of the difference between the different levels of experience also shows a significant difference. The percentage of time spent on fixing compilation errors was 56.37% for the lambda group while it was 44.2% for the control group with 3.5% of the variance being explained by the group difference. 45.7% of the variance in the sample was explained by the difference between the level of education. Therefore, this study suggests that earlier findings that student results are comparable with the results of professional developers are to be considered carefully

Foundations of Empirical Software Engineering: The Legacy of Victor R. Basili

This book captures the main scientific contributions of Victor R. Basili, who has significantly shaped the field of empirical software engineering from its very start. He was the first to claim that software engineering needed to follow the model of other physical sciences and develop an experimental paradigm. By working on this postulate, he developed concepts that today are well known and widely used, including the Goal-Question-Metric method, the Quality-Improvement paradigm, and the Experience Factory. He is one of the few software pioneers who can aver that their research results are not just scientifically acclaimed but are also used as industry standards. On the occasion of his 65th birthday, celebrated with a symposium in his honor at the International Conference on Software Engineering in St. Louis, MO, USA in May 2005, Barry Boehm, Hans Dieter Rombach, and Marvin V. Zelkowitz, each a long-time collaborator of Victor R. Basili, selected the 20 most important research papers of their friend, and arranged these according to subject field. They then invited renowned researchers to write topical introductions. The result is this commented collection of timeless cornerstones of software engineering, hitherto available only in scattered publications

Adding reference immutability to Java

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (leaves 129-133).This paper describes a programming language, Javari, that is capable of expressing and enforcing immutability constraints. The specific constraint expressed is that the abstract state of the object to which an immutable reference refers cannot be modified using that reference. The abstract state is (part of) the transitively reachable state: that is, the state of the object and all state reachable from it by following references. The type system permits explicitly excluding fields from the abstract state of an object. For a statically type-safe language, the type system guarantees reference immutability. The type system is distinguishes the notions of assignability and mutability; integrates with Java's generic types and with multi-dimensional arrays; provides a mutability polymorphism approach to avoiding code duplication; and has type-safe support for reflection and serialization. This paper describes a core calculus including formal type rules for the language. Additionally, this paper describes a type inference algorithm that can be used convert existing Java programs to Javari. Experimental results from a prototype implementation of the algorithm are presented.by Matthew S. Tschantz.M.Eng