Foreword

Summary

Programming Languages and Software practice are always engaged in a game of leapfrog: a forward looking programming language introduces new ways of thinking about software development, and its constructs shape the way programmers think about their craft; creative programmers invent new idioms and patterns to tackle ever more complex programming tasks, and these idioms become incorporated in the next generation of programming languages.

The latest version of Ada, whose description we owe once again to the inimitable expository talents of John Barnes, has exemplified this dynamic repeatedly over the last 30 years.

• Ada 83 showed programmers how programming in the large should be organized (packages, strong typing, privacy) and convinced them that indices out of range were not a common pitfall of programming but elementary errors that could be controlled with proper declarations and constraint checking. Ada 83 also put concurrent programming in a mainstream programming language.

• Ada 95 benefited from a decade-long development in object-oriented programming techniques, and successfully grafted the ideas of polymorphism and dynamic dispatching onto a strongly-typed language with concurrency. It enhanced programming-in-the large capabilities with child units and their generic incarnations.

• Ada 2005 showed how data-based synchronization (protected types) and concurrency (task types) could be unified through a novel use of interface inheritance, and adopted a conservative model of multiple inheritance of interfaces that has proved more robust than the more unrestricted models of MI.