[GS] Balanced Ternary is a number system in base 3. Instead of using (0,1,2), this system 
use (-1,0,1) or (-,0,+). These values are called trits (TRInary DigiT).

Numbers are power of 3. For example :

 89 = +81 +9 -1 = +3**4 +3**2 -3**0 = +0+0-

 -78 = -81 +3 = -3**4 +3**1 = -00+0

Here is a simple clock with balanced ternary display. The first line for hours, the second for minutes and the third for seconds.

[Balanced Ternary Clock]
======tcl
# clock-trit.tcl 
# Author:      Gerard Sookahet
# Date:        15 March 2017 
# Description: Balanced ternary clock
# References: https://en.wikipedia.org/wiki/Balanced_ternary

package require Tk
bind all <Escape> exit
font create myDefaultFont -family Consolas -size 32 -weight bold
option add *font myDefaultFont

proc every {ms body} {
 eval $body
 after $ms [list every $ms $body]
}

proc dec2trit n {
 if {$n == 0} {return "0"}
 while {$n != 0} {
      lappend trit [lindex {0 + -} [expr {$n % 3}]]
      set n [expr {$n / 3 + ($n % 3 == 2)}]
 }
 return [join [lreverse $trit] ""]
}
 
pack [label .clock -textvar time -bg darkblue -fg orange]

every 1000 {
 set ::time [join [lmap x {%H %M %S} {dec2trit [scan [clock format [clock sec] -format $x] %d]}] "\n"]
}
======

Balanced ternary has interesting properties :

- The sign of a number is given by its most significant nonzero trit

- To negate a number, you swap - and +, leaving 0 alone

- Comparing any two numbers is performed by reading left-to-right and by using lexicographic order

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