#----------------------------------------------------------------------
# Hanoing puzzle.
# Fernando Rodriguez Villegas.
# Math, puzzles and computers, Spring 2003.
# University of Texas at Austin.
#
# In a unix shell this program runs with the command 
# wish hanoing.tcl
#----------------------------------------------------------------------

# n is the number of buttons on the puzzle, set to 5 by default.

set n 5

# colors is the list of colors the buttons can have (in an arbitrary but fixed 
# cyclic ordering) 

set colors {"white" "red" "blue"}


# This bit of code creates the frame on which the buttons are going to
# be placed. 

frame .f 
grid .f -row 1 -column 0 -columnspan 8

#----------------------------------------------------------------------
# First we put in 3 buttons called e, r and d; e, contains the value
# of n, which can be changed by the user  (though at this point
# decreasing n doesn't work very well); r, is bound to the command
# Reset (defined below), which creates the colored buttons of the
# puzzle; and d, simply quits the whole thing.

entry .f.e -width 3 -textvariable n
button .f.r -text "reset" -command Reset
button .f.d -text "dismiss" -command "destroy ."

# We now place these buttons on the frame.

set i 0

foreach p {e r d} {
grid .f.$p -row 1 -column [expr 2*$i] -columnspan 2
incr i
}

#----------------------------------------------------------------------
# The process Reset (re-)initializes the puzzle.

proc Reset {} {
global n colors

for {set i 1} {$i <= $n} {incr i} {

# We choose a random color from the list of colors.  The whole
# expression [expr {round(3*rand()-.5)}] simply returns a random
# choice of number 0, 1 or 2

    set color [lindex $colors [expr {round(3*rand()-.5)}]]

# This kills the $i-th button if it exists; we need it to redefine the
# button.

    if {[winfo exists .b$i]} {
	destroy .b$i
    }

# We create the $i-th button of the color we picked above (both when
# by itself and when the cursor is over it) and is bound to the
# command Do $i; i.e. when the user clicks this button the process Do
# runs with this value of $i.

button .b$i -height 2 -width 2  -background $color -activebackground $color -command "Do $i"
grid .b$i -row 0 -column [expr {$i - 1}]
}
}

#----------------------------------------------------------------------
# Process Do that is bound to the colored buttons.

proc Do {i} {
global n colors

# The tree questions are encoded in the 0/1 variables test, test1 and
# test2 (in this order).

# First answer is yes unless we need to change it later.

set test 1

# ccolor is the current color of the $i-th button.

set ccolor  [.b$i cget -background]

# Check whether $j-th button with j < i is of same color as current
# one; if any is, change first answer test to 0. (Yes, we should
# use a while loop...)

for {set j 1} {$j < $i} {incr j} {
    if {[.b$j cget -background] == $ccolor} {
set test 0
}   }


# If first answer test is yes proceed further otherwise do nothing.

if {$test} {

# Set second answer test1 to 1.

    set test1 1

# Pick next color in the list and call it ncolor.

    set cindex [lsearch $colors $ccolor]
    set ncolor [lindex $colors [expr {($cindex+1)%3}]]

# Check whether $j-th button with j < i is of the same color as new
# color; if any is, change second answer test1 to 0. (Yes again, we
# should use a while loop...)

    for {set j 1} {$j < $i} {incr j} {
    if {[.b$j cget -background] == $ncolor} {
    set test1 0
}   }   

# If second answer test1 is yes change color of button to new one
# otherwise proceed to third question.

if {$test1} {

# Change color to $i-th button.

    .b$i configure -background $ncolor -activebackground $ncolor

# Try third color.

} else {

# Third answer test2 is yes unless we change it later.

	set test2 1
# New color (again) called ncolor is 2 further down the list from current.

	set ncolor [lindex $colors [expr {($cindex+2)%3}]]

# Check whether $j-th button with j < i is of the same color as new
# color; if any is, change third answer test2 to 0. (Indeed, we
# should...)

    for {set j 1} {$j < $i} {incr j} {
    if {[.b$j cget -background] == $ncolor} {
	set test2 0
    }   
}

# If third answer test2 is yes change color of button to new one
# otherwise we are done.

if {$test2} {
    .b$i configure -background $ncolor -activebackground $ncolor
}   }   }   }

#----------------------------------------------------------------------
# Initialize puzzle.

Reset