Programming in Icon ; Part II — Programming with Co - Expressions

1. Introduction This report is the second in a series that deals with various aspects of programming in Icon. The first report [1] dealt with generators. Co-expressions are the topic of this second report for two reasons: (1) they derive their utility from generators, and (2) they seem to present more problems to programmers than other features of Icon. The first two parts of this report treat the basic aspects of co-expressions and their common uses. The third part describes the use of co-expressions to provide programmer-defined control operations. More advanced uses of co-expressions are covered in the final part. Appendices contain examples illustrating programming techniques and exercises for interested readers. This report assumes a familiarity with Version 6 of Icon [2], although co-expressions themselves are described in detail here. A good understanding of generators [1] is a prerequisite for the material that follows. Some features of co-expressions that are described in this report were added in Version 6.4 of Icon. Such features are noted.