Playing with bits
Richard Suchenwirth 2002-12-07: Here is another educational Tcltoy: a set of 8 checkboxes that represent the bits of a byte. Each is labeled with its positional value below. The button at bottom displays the current value of the byte in hexadecimal, octal and decimal. Clicking on it resets all bits to 0, or, if they already are, to 1.
Changes
- PYK 2016-01-15
- Fixed a bug the reset proc, eliminated calls to eval, and widgetified so to allow multiple instances of this widget in one application. The code grew, but not by much considering the additional functionality. I attempted to use focus to make the widget behave as I imagine is expected, and change the behaviour from restarting on <Escape> to destroying and recreating the GUI elements on <Escape>. Made analagous changes to the widget by JJM at the bottom of this page.
Description
The simple code below contains some tricks that are unique to Tcl. The positional values of the 8 bits serve as variable names as well, and with prefixed "." as widget names of the checkboxes. The two procedures first import the global list of positional values, then via eval global each of them separately. As name and onvalue of a "bit" are the same, the otherwise puzzling command
set $i $i
makes perfect sense - if i is 16, it assigns the value 16 to the variable 16...
Code
#! /usr/bin/env tclsh
package require Tk
proc bitplay master {
set name [info cmdcount]
namespace eval $name {} {
namespace ensemble create
namespace export *
proc ~ {} {
namespace delete [namespace current]
}
proc init {} {
variable master
variable positionalValues {128 64 32 16 8 4 2 1}
foreach i $positionalValues {
checkbutton $master.$i -variable [namespace current]::$i \
-onvalue $i -command [namespace which compute]
lappend buttons $master.$i
lappend labels [label $master.l$i -text $i]
}
grid {*}$buttons
grid {*}$labels
button $master.result -textvar [namespace current]::result \
-command [namespace which reset] -borderwidth 1
foreach child [winfo children $master] {
bindtags $child [linsert [
bindtags $child] 1 [namespace current]]
}
keybindings [namespace current]
keybindings $master
bind $master <Destroy> [namespace code ~]
grid $master.result -columnspan 8 -sticky ew
focus $master
compute ;# show the initial state (should be 0)
}
proc keybindings w {
bind $w <Escape> [namespace code restart]
}
proc reset {} {
variable positionalValues
variable result
foreach i $positionalValues {
variable $i
if {[lindex $result end-1] == 0} {
set $i $i
} else {set $i 0}
}
compute
}
proc compute {} {
variable positionalValues
variable result
set res 0
foreach i $positionalValues {
variable $i
incr res [set $i]
}
set result [
format "Hex: 0x%02X, Octal: 0o%02o, Decimal: %d (%c)" \
$res $res $res $res]
}
proc restart {} {
variable master
destroy {*}[winfo children $master]
after 2 [list after idle [list [namespace which init]]]
}
set master [uplevel set master]
}
$name keybindings $master
bind $master <ButtonPress> [list focus $master]
$name init
return $name
}
#bind . <Escape> {exec [info nameofexecutable] $argv0 &; exit}
frame .bitplay
grid .bitplay
bitplay .bitplay JJM 2002-12-09: Fixed typo in the hex and octal format strings. - RS: Thanks! I originally started this at home in all leisure, but when at work I hurriedly try to insert fixes (and don't test well - the screenshot above still shows the octal bug!), such things happen... Thanks again for attention, and new ideas!
JJM 2002-12-09: By changing these lines:
grid .result -columnspan 8 -sticky ew set result [format "Hex: 0x%2X, Octal: 0o%02o, Decimal: %d (%c)" $res $res $res $res]
to these:
grid .result -columnspan [llength $positionalValues] -sticky ew set result [format "Hex: 0x%02X, Octal: 0o%02o, Decimal: %d" $res $res $res]
You can add an arbitrary number of values to the positionalValues list and the code will still work properly.
It looks like this:
JDR 2007-01-08: Give this a try.
Replace this line
set positionalValues {128 64 32 16 8 4 2 1}With this for loop, set i to whatever number you want to a maximum value of 31.
for {set i 31} {$i > 0} {incr i -1} {
lappend positionalValues $i
}Replace this line
checkbutton .$i -variable $i -onvalue $i -command compute
With this
checkbutton .$i -variable $i -onvalue [expr {int(pow(2,($i - 1)))}] -command computeReplace this line
set $i $i
With this
set $i [expr {int(pow(2,($i - 1)))}]One final note, you might want to change the positionalValues name to positionalLabels
JJM 2002-12-09, Far more radical modifications:
#! /usr/bin/env tclsh
package require Tk
proc mbitplay master {
set name [info cmdcount]
namespace eval $name {
namespace ensemble create
namespace export *
set positionalValues(1) {0x00000008 0x00000004 0x00000002 0x00000001}
set positionalValues(2) {0x00000080 0x00000040 0x00000020 0x00000010}
set positionalValues(3) {0x00000800 0x00000400 0x00000200 0x00000100}
set positionalValues(4) {0x00008000 0x00004000 0x00002000 0x00001000}
set positionalValues(5) {0x00080000 0x00040000 0x00020000 0x00010000}
set positionalValues(6) {0x00800000 0x00400000 0x00200000 0x00100000}
set positionalValues(7) {0x08000000 0x04000000 0x02000000 0x01000000}
set positionalValues(8) {0x80000000 0x40000000 0x20000000 0x10000000}
proc compute {} {
variable positionalValues
variable result
set res 0
foreach j [lsort -integer [array names positionalValues]] {
foreach i $positionalValues($j) {
variable $i
set res [expr {wide($res) + wide([set $i])}]
}
}
set result [format "Hex: 0x%02X, Octal: 0o%02o, Decimal: %ld" \
$res $res $res]
}
proc ~ {} {
namespace delete [namespace current]
}
proc init {} {
variable master
variable positionalValues
set row 0
foreach j [lsort -integer [array names positionalValues]] {
set buttons {}
set labels {}
foreach i $positionalValues($j) {
checkbutton $master.$i -variable [namespace current]::$i \
-onvalue $i -command [namespace code compute] \
-borderwidth 2
lappend buttons $master.$i
lappend labels [label $master.l$i -text $i]
}
eval grid $buttons -row $row -columnspan [
llength $positionalValues(1)]
eval grid $labels -row [expr {$row + 1}] -columnspan [
llength $positionalValues(1)]
set row [expr {$row + 2}]
}
bind $master <Destroy> [namespace code ~]
button $master.result -textvar [namespace current]::result \
-command [namespace code reset] -borderwidth 1
foreach child [winfo children $master] {
bindtags $child [linsert [
bindtags $child] 1 [namespace current]]
}
grid $master.result -row [expr {$row + 2}] -columnspan [
expr {[llength $positionalValues(1)] * 4}] -sticky ew
keybindings [namespace current]
focus $master
compute ;# show the initial state (should be 0)
}
proc keybindings w {
bind $w <Escape> [namespace code restart]
}
proc reset {} {
variable positionalValues
variable result
foreach j [lsort -integer [array names positionalValues]] {
eval global $positionalValues($j)
foreach i $positionalValues($j) {
variable $i
if {[lindex $result end] == 0} {
set $i $i
} else {
set $i 0
}
}
}
compute
}
proc restart {} {
variable master
destroy {*}[winfo children $master]
after 0 [list after idle [list [namespace which init]]]
}
set master [uplevel set master]
}
$name init
$name keybindings $master
return $name
}
frame .mbitplay
grid .mbitplay
mbitplay .mbitplay escargo 2005-08-16: Changed the last format statement to use positional specifiers instead of sequential ones.
AMG: Relax with bits! 
