[incr Tcl] is a free development and IT software utility that enables you to enhance your Tcl usage. First developed by Michael McLennan, this program is a set of object-oriented extensions for the Tcl programming language. Its name is a pun on C++ and  is also stylized as “itcl” and “intr Tcl.”

[incr Tcl] is widely used as it provides the extra language support needed to build large Tcl/Tk applications. It provides a similar object model, including multiple inheritance, public and private classes, and variables. However, you’ll need to be familiar with Tcl and even C++ to use it properly.

A handy little tool

Tcl—pronounced as "tickle" or simply called with its letters—is a high-level, general-purpose, interpreted, and dynamic programming language. It was designed with the goal of being very simple and compact but powerful, casting everything into the mold of a command. As such, it’s quite popular to use the combination of Tcl and the Tk extension—a.k.a. Tcl/Tk—which enables building a graphical user interface natively in Tcl.

However, as applications get larger, Tcl/Tk code becomes more and more difficult to understand, maintain, and extend. This is where [incr Tcl] comes in. At its core, this utility is a Tcl extension that adds object-oriented programming constructs to the aforementioned programming language. By doing so, the resulting code processed by this extension is much easier to understand and maintain for Tcl/Tk.

In more detail, “objects” are used as the building blocks for an application. These are a bag of data with a set of procedures. Objects are then organized into "classes" with identical characteristics and classes can inherit functionality from one another. However, you’ll need to be familiar with using Tcl first to operate [incr Tcl] well. There’s extensive online documentation available for it but it can overwhelm beginners.

Requires foreknowledge

All in all, [incr Tcl] is a tool well-loved by the Tcl for its great features and ease of use. While you’ll have to know much about how Tcl works first—and preferably, even C++, as well—it’s worth the effort as this software makes it much easier and quicker to work with codes the bigger your projects are. This is a highly recommended utility program.