Visual TAL

Richard Suchenwirth 2013-12-01 - Last night on the Tclers' Chat, stu challenged me to write a visual emulator for TAL. Challenge accepted, after some 3 hours here is (another iteration of) the initial code that managed to step (with the <Down> key) through the TAL code emulating hypot. A day later, the "Run" button was also enabled to, well, run the code (waiting 500 ms between steps, so one can visually follow somewhat), and stop at breakpoints where set.

On top you can enter a proc (with fixed name "f"), hit <Return> to get its body dis- and reassembled.

In the main window at left you see the TAL source code (ready to assemble, hopefully) in black, while the disassemble code is added as comments in red (just in case dis2asm did something wrong). The yellow highlighting marks the code that will be executed next. The window is editable, and "what you see is what is executed", because the code to execute is fetched directly before execution from the highlighted line.

On the right the local variables are displayed (you can edit their values), and below that the current stack.


Of the 130 TAL instructions, about 50 have been implemented so far (see the function vtal.eval below). The underlying idea is that you will also be able to edit the displayed TAL source, and run it again... lots of bells and whistles in planning...

Following is the evening edition for 2013-12-03. New feature: set a breakpoint by right-clicking, shows this stop sign stop.gif. Delete a breakpoint just like a character :^) It took me a while to get it correct, but finally.. just 10 extra LOC! That's certainly worth it ;^)

Disclaimer: While the real TAL assembler implements beginCatch and endCatch, this emulator doesn't yet, so no catch here for the time being... Also missing: dict instructions (will come), array instructions (more difficult, as variables are now managed in an array - needs redesign...), TclOO, coroutine...

For the moment, just consider this an educational tool for a subset of Tcl :^) I'll keep the latest tal.tcl on that page, so you don't need to stitch it together from the various dis2asm pages.

#!/usr/bin/env tclkit
# vtal.tcl -- Visual TAL

set thisdir [file dirname [info script]]
source $thisdir/tal.tcl
package require Tk
image create photo stop -file $thisdir/stop.gif

proc vtal {{w ""}} {
    wm title . "Visual TAL"
    global g
    set g(stack) ---bottom---
    set g(bp) 0
    if {$w ne ""} {pack [frame $w] -fill both -expand 1}
    pack [frame $] -side top
    button $ -text "Step" -command vtal.step
    set g(run) $
    button $ -text Run -command
    button $ -text Reset -command vtal.reset
    label $ -text "proc f " -background white
    entry $ -width 80 -textvar g(entry)
    bind  $ <Return> vtal.refresh
    eval pack [winfo children $] -side left -fill y
    pack [label $ -textvariable g(Info)] -side bottom
    set g(Info) "Welcome to Visual TAL"
    pack [frame $w.right] -side right -fill both -expand 1
    pack [label $w.right.1 -text "Local variables" -relief raised] -fill x
    set g(vars) $w.right.vars
    pack [frame $g(vars)] -fill x
    pack [label $w.right.2 -text Stack -relief raised] -fill x
    pack [text $w.right.stack -width 32] -fill both -expand 1
    set g(stk) $w.right.stack
    pack [scrollbar $w.y -command "$w.t yview"] -side right -fill y
    pack [text $w.t -wrap word \
              -width 72 -yscrollcommand "$w.y set"] -fill both -expand 1
    $w.t tag configure hilite -background yellow
    set g(txt) $w.t
    bind $w.t <3> {breakpoint %W %x %y}
    foreach i {red blue} {$w.t tag configure $i -foreground $i}
    bind all <Down> vtal.step
    bind all <F9> {console show}
proc breakpoint {w x y} {
    set pos [expr int([$w index @$x,$y])]
    $w image create $pos.0 -image stop
proc vtal.reset {} {
    global g slot
    vtal.hilite $g(txt) 2
    set g(stack) ---bottom---
    set g(Info) Ready.
    foreach {num descr} [array get slot] {
        if ![string match *arg,* $descr] {
            if [string match *temp* $descr] {
                set name $num
            } else {set name [lindex $descr end]}
            set g(var,$name) ""
proc vtal.refresh {{function ""}} {
    global g slot
    if {$function ne ""} {set g(entry) $function}
    array unset g var,*
    if [catch [list eval [linsert $g(entry) 0 proc f]] msg] {error $msg}
    foreach {argl} $g(entry) break
    array unset slot
    set asm [dis2asm [disasm proc f]]
    set res [list proc f $argl [list asm $asm]]
    set rc [catch $res msg] $g(txt) $res
    if {$rc != 0} {error $msg}
proc {} {
    global g
    $g(run) configure -text Stop -command vtal.stop
    every $g(delay) vtal.step
set g(delay) 200
proc every {ms body} {uplevel #0 $body; after $ms [namespace code [info level 0]]}
proc vtal.stop {} {
    global g
    foreach id [after info] {after cancel $id}
    $g(run) configure -text Run -command
proc {w str} {
    $w delete 1.0 end
    foreach line [split $str \n] {
        if {[regexp {^(proc|\})} $line]} {
            $w insert end $line\n blue
        } else {
            foreach {code cmt rest} [split $line #] break
            set code [string trimright $code ";"]
            if {$cmt ne ""}  {set cmt ";#$cmt"}
            if {$rest ne ""} {set rest #$rest}
            $w insert end $code "" $cmt red $rest\n red 
    $w tag add hilite 2.0 2.end
proc vtal.vars {} {
    global g slot
    set w $g(vars)
    eval destroy [winfo children $w]
    set i 0
    foreach num [lsort -dict [array names slot]] {
        set lvar $slot($num)
        set varname [lindex $lvar end]
        if {$varname eq "temp"} {set varname $num}
        grid [label $w.[incr i] -text "%v$num: $lvar"] \
            [entry $w.[incr i] -textvariable g(var,$varname)] -sticky w
proc vtal.step {} {
    global g
    set w $g(txt)
    foreach {from to} [$w tag ranges hilite] break
    if ![info exists from] return
    set lineno [lindex [split $from .] 0]
    set cmd [$w get $from $to]
    if {[string match \}* $cmd] || $g(bp)==0 && [scan [$w get $lineno.0] %c] eq ""} {
        set g(bp) 1
        after 1 vtal.stop
    incr lineno
    set g(Info) $cmd
    set lineno [vtal.eval $cmd $lineno]
    set g(bp) 0
    vtal.hilite $w $lineno
proc vtal.eval {cmd line} {
    global g
    foreach part [split $cmd ";"] {
        if [string match #* [string trim $part]] {return $line}
        foreach {instr arg1 arg2} $part break
        if ![info exists instr] {return $line}
        set tos [lindex $g(stack) 0] ;# top of stack
        switch $instr {
            add              {push [expr {[pop] + [pop]}]}
            append           {append g(var,$arg1) $tos}
            bitand           {push [expr {[pop] & [pop]}]}
            bitnot           {push [expr {~ [pop]}]}
            bitor            {push [expr {[pop] | [pop]}]}
            bitxor           {push [expr {[pop] ^ [pop]}]}
            concat           {push [vtal.concat $arg1]}
            currentNamespace {push [namespace current]}
            div              {pop x; push [expr {[pop] / $x}]}
            dup              {push $tos}
            eq               {push [expr {[pop] == [pop]}]}
            existArrayStk    {pop x; push [info exists [set x]([pop])]}
            exist            {push [info exists $arg1]}
            expon            {pop x; push [expr {[pop]**$x}]}
            ge               {pop x; push [expr {[pop] >= $x}]}
            gt               {pop x; push [expr {[pop] > $x}]}
            incr             {push [expr {[pop] + $arg1}]}
            incrImm {push [ $arg1 [expr {[vtal.load $arg1] + $arg2}]]}
            invokeStk  {push [vtal.invoke $arg1]}
            jump       {set line [vtal.jump $arg1]}
            jumpTrue   {if {[pop] != 0} {set line [vtal.jump $arg1]}}
            jumpFalse  {if {[pop] == 0} {set line [vtal.jump $arg1]}}
            label      {}
            lappend    {lappend g(var,$arg1) $tos}
            land       {pop x; push [expr {[pop] && $x}]}
            list       {push [vtal.list $arg1]}
            listIn     {pop x; push [expr {[pop] in $x}]}
            listIndex  {pop x; push [lindex [pop] $x]}
            listLength {push [llength [pop]]}
            listNotIn  {pop x; push [expr {[pop] ni $x}]}
            load       {push [vtal.load $arg1]}
            lor        {pop x; push [expr {[pop] || $x}]}
            lshift     {pop x; push [expr {[pop] << $x}]}
            le         {pop x; push [expr {[pop] <= $x}]}
            lt         {pop x; push [expr {[pop] < $x}]}
            mod        {pop x; push [expr {[pop] % $x}]}
            mult       {push [expr {[pop] * [pop]}]}
            neq        {push [expr {[pop] != [pop]}]}
            nop        {}
            not        {push [expr {! [pop]}]}
            pop         pop
            push       {push $arg1}
            rshift     {pop x; push [expr {[pop] >> $x}]}
            store      { $arg1 $tos}
            strcmp     {pop x; push [string compare [pop] $x]}
            streq      {push [string equal [pop] [pop]]}
            strfind    {pop x; push [string first [pop] $x]}
            strindex   {pop x; push [string index [pop] $x]}
            strlen     {push [string length [pop]]}
            strmap     {pop x; push [string map [pop] $x]}
            strmatch   {pop x; push [string match [pop] $x]}
            strneq     {push [expr ![string equal [pop] [pop]]]}
            strrange   {push [string range [pop] $arg1 $arg2]}
            strrfind   {pop x; push [string last [pop] $x]}
            sub        {pop x; push [expr {[pop] - $x}]}
            tryCvtToNumeric {}
            uminus     {push [expr {-[pop]}]}
            unset      {unset $arg1}
            ""         {}
            default   {vtal.stop; error "instruction $part not yet implemented"}
    return $line
proc vtal.concat num {
    set res {}
    while {$num > 0} {
        set res [pop]$res
        incr num -1
    return $res
proc vtal.list num {
    set res {}
    while {$num > 0} {
        set res [linsert $res 0 [pop]]
        incr num -1
    return $res
proc vtal.invoke num {
    set cmd {}
    while {$num > 0} {
        set cmd [linsert $cmd 0 [pop]]
        incr num -1
    catch $cmd res
    return $res
proc vtal.jump label {
    global g
    set pos [$g(txt) search "label $label" 1.0]
    if {$pos eq ""} {error "label $label not found"}
    set line [lindex [split $pos .] 0]
proc vtal.load   name        {return $::g(var,$name)}
proc {name value} {
    if ![info exists ::g(var,$name)] {error "no local variable $name"}
    set ::g(var,$name) $value
proc pop {{_v ""}} {
    global g
    set res [lindex $g(stack) 0]
    if {$res eq "---bottom---"} {error "stack underflow"}
    set g(stack) [lrange $g(stack) 1 end]
    if {$_v ne ""} {upvar 1 $_v var; set var $res}
    return $res
proc push what {
    global g
    set g(stack) [linsert $g(stack) 0 $what]
proc vtal.showstack {} {
    global g
    $g(stk) delete 1.0 end
    $g(stk) insert 1.0 [join $g(stack) \n]
proc vtal.hilite {w line} {
    $w tag remove hilite 1.0 end
    $w tag add hilite $line.0 $line.end+1c
    $w see $line.0

#-- demo function for starters
#vtal.refresh {{x y} {expr {$x%2? acos(-1) : sqrt(2)}}}
#vtal.refresh {x {foreach i $x {puts ($i)}}}
vtal.refresh {x {set res {};foreach i $x {if {$i>0} {lappend res $i}};set res}}