Chapter 14. Namespaces

Namespaces group procedures and variables into separate name spaces. Namespaces were added in Tcl 8.0. This chapter describes the namespace and variable commands.

Namespaces provide new scopes for procedures and global variables. Originally Tcl had one global scope for shared variables, local scopes within procedures, and one global namespace for procedures. The single global scope for procedures and global variables can become unmanageable as your Tcl application grows. I describe some simple naming conventions on page 171 that I have used successfully in large programs. The namespace facility is a more elegant solution that partitions the global scope for procedure names and global variables.

Namespaces help structure large Tcl applications, but they add complexity. In particular, command callbacks may have to be handled specially so that they execute in the proper namespace. You choose whether or not you need the extra structure and learning curve of namespaces. If your applications are small, then you can ignore the namespace facility. If you are developing library packages that others will use, you should pick a namespace for your procedures and data so that they will not conflict with the applications in which they are used.