The design of Apple—A language for modular programs

Sometimes programming is difficult because of the amount of detail that is relevant to the problem being solved. A suitable language for these problems should aid the programmer in organizing a program as a synthesis of parts. Apple is a language designed for such applications. It is a typed language in which functions are objects, and it provides three complementary ways to modularize programs. These are the definition of environments, the use of functional abstraction, and the use of data abstraction or parameterized, abstract data types.In this paper we describe the main features of Apple, and explain the motivation for many of the design decisions. Another document furnishes a formal definition.