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setting up and using a namespace
Libraries, Packages and Namespaces example from a Well House Consultants training course
More on Libraries, Packages and Namespaces [link]

This example is described in the following article(s):
   • What is a namespace and why do we need them? - [link]

Source code: nsp Module: T213
# setting up and using a namespace

# The following code is in its own namespace, which allows just one name
# (we have chosen table) to be brought into the main program, yet we can
# bring in lots of code

namespace eval table {

# variable names used within a namespace are taken to be members of that
# namespace, unless a specific namespace is stated. There's one example
# of that here - ::ticker is a variable at the top level namespace.

variable ncalls 0

proc area {w h} {
        variable ncalls
        incr ncalls
        append ::ticker "!"
        set a [expr $w * $h]
        return $a
        }

proc peri {w h} {
        variable ncalls
        incr ncalls
        append ::ticker "@"
        set p [expr 2 * ($w + $h)]
        return $p
        }

proc doggie {w h} {
        variable ncalls
        incr ncalls
        append ::ticker "%"
        set d [expr (($w > $h) ? $h : $w) /2.0]
        return $d
        }
}

# ---------------------------------------------------------------

# Main program in the top level namespace. Anything that's in the
# namespace we've defined above needed table:: in front of it (you
# can do it other ways with export and imports, but that would make
# this little demo program more obfurscated!)

set ticker ">"

set wid 100
set hei 50

set ar [table::area $wid $hei]
set ap [table::peri $wid $hei]
set ad [table::doggie $wid $hei]

puts "Results are $ar $ap $ad $table::ncalls"
puts "Trace ... $ticker"

exit

------------------- Here's how that runs:

munchkin:ta grahamellis$ tclsh nsp
Results are 5000 300 25.0 3
Trace ... >!@%
munchkin:ta grahamellis$


Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Tcl
 * Tcl Programming
 * Tcl Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Tcl, Tk and Expect are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Libraries, Packages and Namespaces" training module. You'll find a description of the topic and some other closely related examples on the "Libraries, Packages and Namespaces" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
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