Itcl

Itcl, short for incr Tcl, is an object-oriented extension to the Tcl scripting language that adds class-based programming capabilities. It was one of the earliest OO extensions for Tcl and helped establish object-oriented practices within the Tcl community. Itcl provides a compact, self-contained set of OO constructs that integrate with Tcl code, allowing developers to define classes, create and manipulate objects, and organize code around data and behavior.

Key features include class definitions, instance variables, and methods, as well as constructors and destructors. Itcl supports inheritance, enabling derived classes to extend or override behavior from base classes, and dynamic method dispatch. It also provides access control mechanisms to manage visibility of members, and supports features such as object lifecycle management and event-related programming within the Itcl object system.

Usage typically involves loading the Itcl package into a Tcl interpreter with a package require statement and then writing class definitions using Itcl’s syntax. After defining a class, objects can be instantiated and their methods invoked from Tcl code, with Itcl providing a bridge between Tcl’s scripting and object-oriented concepts.

Historical notes and current status: Itcl originated in the 1990s as a foundational OO extension for Tcl. While Tcl has since added its own built-in object system (TclOO) in newer versions, Itcl remains available for legacy projects and for developers who prefer its older design or syntax. Itcl has seen multiple maintenance releases and continues to be used in various Tcl projects alongside newer OO approaches.