Practical Programming in Tcl & Tk, Third Edition

Using Namespaces

Namespaces add new syntax to procedure and variable names. A double colon, ::, separates the namespace name from the variable or procedure name. You use this syntax to reference procedures and variables in a different namespace. The namespace import command lets you name things in other namespaces without the extra syntax. Namespaces can be nested, so you can create a hierarchy of scopes. These concepts are explained in more detail in the rest of this chapter.

One feature not provided by namespaces is any sort of protection, or a way to enforce access controls between different namespaces. This sort of thing is awkward, if not impossible, to provide in a dynamic language like Tcl. For example, you are always free to use namespace ...