Richard Suchenwirth - "Creative writing" in this context means assigning a value (writing) to a variable referred to by name, that is created if it doesn't exist. The following Tcl commands are "creative writers": array set - foreach - gets - lappend - regexp - regsub - scan - set
When code is evaluated in a namespace, but outside of a proc, the namespace rule for name resolution applies: If you provide a fully-qualified name that starts with a ::, there is no question about what command, variable, or namespace you mean. However, if the name does not start with a :: (i.e., is relative), Tcl follows a fixed rule for looking it up: Command and variable names are always resolved by looking first in the current namespace, and then in the global namespace. (TclHelp, namespace man page)
This leads to dangerous context-dependency: depending on what global variables exist, new variables are created either here or there. Ronnie Brunner wrote in the comp.lang.tcl newsgroup:
% set a "global"
global
% namespace eval foo {set a "namespace"; set b "namespace"}
namespace
% set a
namespace
% set foo::a
can't read "foo::a": no such variable
% set b
can't read "b": no such variable
% set foo::b
namespaceHemang Lavana commented: To be safe, you should always use the `variable' command first to declare a variable in the current namespace.
RS: But still, this requirement for a declaration is not in the spirit of Tcl.
Proc definitions inside a namespace remain in that namespace, however; they don't go out to the global namespace, as Ronnie further showed:
% proc a {} {puts global}
% namespace eval foo {proc a {} {puts namespace};proc b {} {puts namespace}}
% a
global
% foo::a
namespace
% b
ambiguous command name "b": binary break
% foo::b
namespaceRS: I think namespace resolution should distinguish between locating existing things (procs or variables) and determining an absolute name for non-existing things.