Version 2 of A simple GUI for decision trees
Updated 2008-02-25 09:31:08 by arjenArjen Markus (20 february 2008) A question from a colleague inspired me to write the program below and the associated example. The question was related to making an easy-to-use system for analysing problems that may require either a simple computation in, say, a spreadsheet, or a much more sophisticated approach using advanced numerical modelling.
The client wants an answer fast, so the system would ask a bunch of questions to decide what solution method is appropriate - a decision tree, so to speak. Simple cases can be dealt with via simple computations, for more complex cases the client is advised to follow the sophisticated path.
Anyhow, such a system in this day and age requires a graphical user-interface and quite likely a web-oriented user-interface. While I did not do the latter bit yet, the first bit was easy enough. For the statistics:
- Requirements analysis and design: slightly less than 1 hour (using pen and paper)
- Coding the first version: approximately 1 hour (admitted: little attention paid to beautifying the GUI layout)
- Testing and debugging via a simple example: again 1 hour
Note that the program uses some more or less subtle namespace manipulations to keep the program's variables away from the user-defined ones.
With the program and the example below you get the following screens:
The use is simple:
- Implement the decision tree and the associated computations in a way as shown by the example
- Run the general program with the file containing that decision tree as an argument
The program itself looks like this:
# decision.tcl --
# Program to define and show GUIs for decision trees
#
# Decide --
# Namespace for running the GUI and associated computations
#
namespace eval ::Decide {
# Private namespace
namespace eval v {
variable previous_window
variable window
variable window_title
variable wcount
set previous_window {}
set wcount 0
}
}
# window --
# Define a new window
#
# Arguments:
# name Name of the window
# title Title
# contents Script defining the contents of the window
#
# Result:
# None
#
# Side effects:
# Entry in array window filled
#
proc ::Decide::window {name title contents} {
set v::window($name) $contents
set v::window_title($name) $title
}
# text --
# Define/show a text label
#
# Arguments:
# string String to present
# second Second string if any
#
# Result:
# None
#
# Side effects:
# Label widget created
#
proc ::Decide::text {string {second {}}} {
if { $second eq "" } {
label .frame1.label$v::wcount -text $string -font "Helvetica, 14"
grid .frame1.label$v::wcount - -sticky news
} else {
set l1 $v::wcount
incr v::wcount
set l2 $v::wcount
label .frame1.label$l1 -text $string -font "Helvetica, 14"
label .frame1.label$l2 -text $second -font "Helvetica, 14"
grid .frame1.label$l1 .frame1.label$l2 -sticky news
}
incr v::wcount
}
# entry --
# Define/show an entry widget
#
# Arguments:
# string String to present
# name Variable name
#
# Result:
# None
#
# Side effects:
# Label widget created
#
proc ::Decide::entry {string name} {
set l1 $v::wcount
incr v::wcount
set e1 $v::wcount
::label .frame1.label$l1 -text $string -font "Helvetica, 14"
::entry .frame1.entry$e1 -textvariable ::Decide::$name -font "Helvetica, 14"
::grid .frame1.label$l1 .frame1.entry$e1 -sticky news
incr v::wcount
}
# choice --
# Define/show a set of radio buttons
#
# Arguments:
# name Name of the associated variable
# choices List of values and descriptive texts
#
# Result:
# None
#
# Side effects:
# Set of radio buttons created
#
proc ::Decide::choice {name choices} {
if { ![info exists ::Decide::$name] } {
set ::Decide::$name [lindex $choices 0]
}
foreach {value text} $choices {
radiobutton .frame1.radio$v::wcount -variable ::Decide::$name -text $text \
-value $value -font "Helvetica, 14"
grid .frame1.radio$v::wcount -sticky nw
incr v::wcount
}
}
# button --
# Define/show a pushbutton
#
# Arguments:
# type Type of button
# command Command associated with it (optional)
#
# Result:
# None
#
# Side effects:
# Pushbutton created
#
proc ::Decide::button {type {command {}}} {
switch -- $type {
"previous" {
set command "::Decide::previousWindow"
set text "<<"
}
"next" {
set text ">>"
}
"done" {
set command "exit"
set text "Done"
}
default {
tk_messageBox -code error -message "Unknown button type: $type"
exit
}
}
::button .frame2.button$v::wcount -text $text -font "Helvetica, 14" \
-command [list namespace eval ::Decide $command]
append v::buttons ".frame2.button$v::wcount "
incr v::wcount
}
# show --
# Show a particular window
#
# Arguments:
# name Name of the window
#
# Result:
# None
#
# Side effects:
# Entry in array window filled
#
proc ::Decide::show {name} {
if { [info exists v::window($name)] } {
foreach child [winfo children .frame1] {
destroy $child
}
foreach child [winfo children .frame2] {
destroy $child
}
set v::wcount 0
set v::buttons {}
namespace eval ::Decide $v::window($name)
if { $v::buttons ne "" } {
eval grid $v::buttons
}
} else {
tk_messageBox -type ok -icon error -message "No window defined by the name '$name'"
exit
}
wm title . $v::window_title($name)
lappend v::previous_window $name
}
# previousWindow --
# Show the previous window
#
# Arguments:
# None
#
# Result:
# None
#
# Side effects:
# Previous window shown and "previous_window" updated
#
proc ::Decide::previousWindow {} {
set prev [lindex $v::previous_window end-1]
set v::previous_window [lrange $v::previous_window 0 end-2]
show $prev
puts >>$v::previous_window<<
}
# mainWindow --
# Set up the main window
#
# Arguments:
# None
#
# Result:
# None
#
# Side effects:
# Main window set up with two frames
#
proc ::Decide::mainWindow {} {
wm geometry . 400x250
frame .frame1
frame .frame2
pack .frame1 -side top -fill x -padx 4
pack .frame2 -side bottom -fill x -padx 4
}
# main --
# test the code so far
#
if { 0 } {
::Decide::mainWindow
::Decide::window x "Title" {
text "Welcome to this simple"
text "Decision tree"
choice v {
red "Red"
blue "Blue"
green "Green text"
}
button next {
show y
}
}
::Decide::window y "Title" {
text "The end"
button previous
button done
}
::Decide::show x
}
::Decide::mainWindow
namespace eval ::Decide {
source [lindex $argv 0]
} The simple example:
# example.app --
# Simple example of the application of "decision.tcl":
# Compute the area and volume of three simple geometrical
# shapes
#
window "type" "Select the type" {
text "Type of geometrical body:"
choice type {
cube "Cube"
block "Block"
sphere "Sphere"
}
button next {
show $type
}
}
window "cube" "Size of the cube" {
text "Please enter the side of the cube:"
entry "Size: " size
button previous
button next {
set area [expr {6.0*$size*$size}]
set volume [expr {$size*$size*$size}]
show "result"
}
}
window "block" "Dimensions of the block" {
text "Please enter the three sides of the block:"
entry "Length: " length
entry "Width: " width
entry "Height: " height
button previous
button next {
set area [expr {2.0*($length*$width+$length*$height+$width*$height)}]
set volume [expr {$length*$width*$height}]
show "result"
}
}
window "sphere" "Size of the sphere" {
text "Please enter the radius of the sphere:"
entry "Radius: " radius
button previous
button next {
set area [expr {4.0*acos(-1.0)*$radius*$radius}]
set volume [expr {4.0*acos(-1.0)*$radius*$radius*$radius/3.0}]
show "result"
}
}
window "result" "Area and volume" {
text "Area:" "$area"
text "Volume:" "$volume"
button previous
button done
}
#
# Start the application
#
show "type"