'''`[namespace] upvar`''', a subcommand of [namespace], makes a namespace
[variable] an alias for another variable.



** Synopsis **

    :   '''namespace upvar''' ''namespace otherVar myVar'' ?''otherVar myVar ...''?



** Description **

'''`[namespace] upvar`''' links ''otherVar'' to ''myVar'', after which any
operation on ''otherVar'' is identical to the same operation on ''myVar'', and
vice versa.  ''otherVar'' is resolved relative to ''namespace'', and my contain
[namespace%|%namespace qualifiers].  When `namespace upvar` is used in the
context of a namespace, ''myVar'' is resolved relative to the current
namespace, and always resolves to a namespace variable.  When `namespace upvar`
is used in the context of a procedure, ''myVar'' is resolved relative to the
current [stack frame], and resolves to a local variable in the current frame if
''myVar'' does not contain namespace qualifiers, or to some namespace variable
if it does.

`namespace upvar` is a convenience command that doesn't add any functionality
not previously available with `[upvar]`.  The following are equivalent:

======
set ns ::foo
upvar #0 ${ns}::bar boo
======

and

======
set ns ::foo
namespace upvar $ns bar boo
======

However, the second form is more efficient at the time the link is made, as it requires less string manipulation and parsing.


[DKF]: `namespace upvar` was created to help accelerate [Snit].



** See Also **

   [namespace]:   the primary command for working with namespaces

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