This book has a number of objectives. First, it provides the concepts and a language to produce sophisticated software. Second, the book tries to make you step back a bit from programming as an activity by highlighting basic problems linked to programming as a discipline. In the end, we hope to share our own pleasure in programming.

The language we use—Caml—makes it possible to achieve all these goals. Caml belongs to the family of “functional” languages, all of which have the following qualities:

• They are particularly well adapted to writing applications for “symbolic computation”—the kind of computing that concerns computer scientists as well as mathematicians—in software engineering, artificial intelligence, formal computation, computer-aided proof, and so forth.

• Functional languages are built on a fundamental theory that derives from mathematical logic. This basis provides these languages with their semantics as well as their systems of types and proof.

• By the very way in which they are designed, these languages support a certain aesthetic in programming, an aesthetic which, like the aesthetic of a mathematical proof, is often an indication of their quality.

This book grew primarily out of a programming course given by Guy Cousineau at the Ecole Normale Supérieure between 1990 and 1995. The book also benefited from the teaching experience of Michel Mauny, who wrote Chapters 8 and 13 and contributed to the overall consistency of the book.