An informal tutorial on Joy

Summary

You are here: An informal tutorial on JoyAn informal tutorial on Joy Back to Main page for the programming language Joy An informal tutorial on Joy by Manfred von Thun Revised February 2003 This revision includes references to John Cowan's (2001) extension. Abstract: Joy is a functional programming language which is not based on the application of functions to arguments but on the composition of functions. It does not use lambda-abstraction of expressions but instead it uses quotation of expressions. A large number of what are called combinators are used to perform dequotation, they have the effect of higher order functions. Several of them can be used to eliminate recursive definitions. Programs in Joy are compact and often look just like postfix notation. Writing programs and reasoning about them is made easy because there is no substitution of actual for formal parameters. This tutorial describes basic features of the language Joy which are likely to be the same in all implementations. Keywords: functional programming, higher order functions, composition of functions, combinators, elimination of recursive definitions, variable free notation Introduction Although the theory of Joy is of interest, this tutorial exposition avoids theory as much as possible. The remainder of this paper is organised as follows: This introductory section continues with a very short outline of some distinguishing features of the language. The next two sections introduce the basic data types and operations on them. The section after that returns to the central feature of Joy: quotations of programs and their use with combinators. After a short section on definitions the next section resumes the discussion of combinators, in particular those that can eliminate the need for recursive definitions. In the final section several short programs and one larger program are used to illustrate programming with aggregates in Joy. To add two integers, say 2 and 3, and to write their sum, you type the...