'''https://github.com/eugenkiss/7guis/wiki%|%7GUIs%|%''' is an interesting project to analyse the usability of different GUI toolkits.  The 7 mini-application examples give focussed examples of important GUI patterns, such that the implementation should serve as a guide to how the language and toolkit under use help or hinder the programmer.

I expect some interesting Tk implementations to appear, perhaps leading to some discussions of where Tk is ''not'' so strong and how it could be improved.

Please add your implementations to this page, or critique ones already here.  Adding a single solution (instead of all 7) is welcome, particularly if it highlights a beautiful technique.
While showing off 3rd-party libraries is encouraged, at least one "naive Tk" implementation of each example should exist.
Though for `Cells` I fully endorse the use of [tablelist], purely on the assumption that no Tk programmer should be without it!

**Naive Tk Implementations**

These are intended to highlight how to use core Tcl/Tk features without relying on 3rd-party libraries.  The code should be self-contained, though relying on bundled extensions such as [ttk], [sqlite3] is not discouraged and [tcllib] / [tklib] dependencies are not out of the question.

Enough "good practice" should be present to make the examples easy to extend or incorporate into a larger program without butchery.  Thus doing everything inside a [namespace], despite the extra verbosity of [namespace which].

***Counter***

======
#!/usr/bin/env tclsh

package require Tk
package require lambda

namespace eval app {
    variable c 0
    entry .e -state readonly -textvariable [namespace which -variable c]
    button .b -text Count -command [lambda@ [namespace current] {} {
        variable c
        incr c
    }]
    pack .e .b -side left
    wm title . Counter
}

wm protocol . WM_DELETE_WINDOW exit
vwait forever
======

***Temperature Converter***

======
#!/usr/bin/env tclsh

package require Tk
package require lambda

namespace eval app {
    variable c 0
    variable f 32

    proc c2f {} {
        puts c2f
        variable c
        variable f
        set f [format %.1f [expr {$c * 9 / 5.0 + 32}]]
    }
    proc f2c {} {
        puts f2c
        variable f
        variable c
        set c [format %.1f [expr {($f - 32) * 5 / 9.0}]]
    }

    entry .c -textvariable [namespace which -variable c]
    entry .f -textvariable [namespace which -variable f]
    label .cl -text "\u00b0 Celcius"
    label .fl -text "\u00b0 Fahrenheit"

    trace add variable c write [lambda@ [namespace current] args c2f]
    trace add variable f write [lambda@ [namespace current] args f2c]

    pack .c .cl .f .fl -side left
}

wm title . "Temperature Converter"
wm protocol . WM_DELETE_WINDOW exit
vwait forever
======

**Your Implementation**

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<<categories>>GUI | Example