Data Structures in the Icon Programming Language

The lcon programming language provides a rich variety of data structures with sophisticated facilities: sets of arbitrary values, tables with associative lookup, lists with positional and deque access mechanisms, and records that extend the type repertoire ofthe language. Instances ofthese structures are created at run-time and grow and shrink as values are added to or removed from them. Storage management is automatic. This paper describes these structures and their use in combination with lcon's goal-directed evaluation mechanism. Examples illustrate the use of pointer semantics and heterogeneity and how the natural geometrical interpretation of structures like trees and graphs in the problem domain is imaged in the programming domain. The work described in this paper u/as supported by National Science Foundation Grants MCS-8 l0 I 9 I ó, DCR-840 I 83 l, DCR-850201 5, and CCR-87 I 3690. @ Computing Systems,Yol.2. No. 4 . Fall 1989 339