Functional C (1997)

The Computer Science Departments of many universities teach a functional language as the first programming language. Using a functional language with its high level of abstraction helps to emphasize the principles of programming. Functional programming is only one of the paradigms with which a student should be acquainted. Imperative, Concurrent, Object-Oriented, and Logic programming are also important. Depending on the problem to be solved, one of the paradigms will be chosen as the most natural paradigm for that problem.

This book is the course material to teach a second paradigm: imperative programming, using C as the programming language. The book has been written so that it builds on the knowledge that the students have acquired during their first course on functional programming, using SML. The prerequisite of this book is that the principles of programming are already understood; this book does not specifically aim to teach ‘problem solving’ or ‘programming’. This book aims to:

• Familiarise the reader with imperative programming as another way of implementing programs. The aim is to preserve the programming style, that is, the programmer thinks functionally while implementing an imperative program.
  
• Provide understanding of the differences between functional and imperative programming. Functional programming is a high level activity. The ordering of computations and the allocation of storage are automatic. Imperative programming, particularly in C, is a low level activity where the programmer controls both the ordering of computations and the allocation of storage. This makes imperative programming more difficult, but it offers the imperative programmer opportunities for optimisations that are not available to the functional programmer.
• Familiarise the reader with the syntax and semantics of ISO-C, especially the power of the language (at the same time stressing that power can kill). We visit all dark alleys of C, from void * to pointer arithmetic and assignments in expressions. On occasions, we use other languages (like C++ and Pascal) to illustrate concepts of imperative languages that are not present in C. C has been chosen because it is a de facto standard for imperative programming, and because its low level nature nicely contrasts with SML. Those who want to learn, for example, Modula-2 or Ada-95 afterwards should not find many difficulties.
• Reinforce the principles of programming and problem solving. This is facilitated by the use of three different languages (mathematics, a functional language, and an imperative language). The fact that these widely differing languages have common aspects makes the idea that programming principles exist and that they are useful quite natural.
  
• Reinforce the principle of abstraction. Throughout the book we encourage the student to look for more abstract solutions, for example, by viewing the signature of a function as an abstraction of its purpose, by using procedural abstractions (in particular higher order functions) early on, and by using data abstraction.
  
• Guide the student from specification and mathematics to implementation and software engineering. In the first chapters the emphasis is on writing correct functions and as we make progress the emphasis gradually shifts to transforming correct functions into efficient and reusable functions. Clean interfaces are of paramount importance, and are sacrificed for better efficiency only as a last resort