Incr Tcl

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Paradigm multi-paradigm: object-oriented, functional, Imperative, event-driven programming
Designed by Michael McLennan
Developer Michael McLennan
First appeared 1993
Stable release
Itcl4.0.0 / 3 February 2013; 4 years ago (2013-02-03)
Typing discipline dynamic typing, everything can be treated as a string
Website incrtcl at sourceforge
Influenced by
Tcl, C++

incr Tcl (commonly stylised as [incr Tcl], and often abbreviated to itcl) is a set of object-oriented extensions for the Tcl programming language. It is widely used among the Tcl community, and is generally regarded as industrial strength[citation needed]. Its name is a pun on "C++". Itcl implementations exist as both a package that may be dynamically loaded by a Tcl application, as well as an independent standalone language with its own interpreter.



Namespace support[edit]

Itcl allows namespaces to be used for organizing commands and variables.


    package require Itcl
    itcl::class Toaster {
        variable crumbs 0
        method toast {nslices} {
            if {$crumbs > 50} {
                error "== FIRE! FIRE! =="
            set crumbs [expr $crumbs+4*$nslices]
        method clean {} {
            set crumbs 0
    itcl::class SmartToaster {
        inherit Toaster
        method toast {nslices} {
            if {$crumbs > 40} {
            return [chain $nslices]
    set toaster [SmartToaster #auto]
    $toaster toast 2

C code integration[edit]

Itcl (like Tcl) has built-in support for the integration of C code into Itcl classes.


Itcl follows the same copyright restrictions as Tcl/Tk. You can use, copy, modify and even redistribute this software without any written agreement or royalty, provided that you keep all copyright notices intact. You cannot claim ownership of the software; the authors and their institutions retain ownership, as described in the "license.terms" files included in the standard distribution. For more information please see

See also[edit]


incr Tcl from the Ground Up by Chad Smith, published in January 2000.

This is a complete reference manual for incr Tcl, covering language fundamentals, OO design issues, overloading, code reuse, multiple inheritance, abstract base classes, and performance issues. Despite its breadth, it follows a tutorial, rather than encyclopedic, approach. This book is out of print as of September 2004.

External links[edit]