The Vesta Language for Configuration Management

Book excerpt: Only information written down in the descrition can influence construction of the system. Nevertheless, the descriptions are concise and easy to read and write. The language evaluator caches the results of evaluating function applications, which are the expensive operations in the Vesta language. Caching in Vesta is automatic and persistent. Because the language is functional and there are no side-effects, cachingis conceptually straightforward. Vesta caches the result of all function applications -- from those at the leaves (e.g., compiling one source file), to those in the middle (e.g., packaging up a library), all the way to the top. Caching function applications at all levels permits Vesta to build and rebuild large software systems efficiently."