Richard Suchenwirth 2005-09-08 - A colleague asked for how to step through Tcl procedures. It didn't take me long to cook up this example, which provides an interactive prompt at which you can inspect the situation in the stepped proc (reinvented from Steppin' out :):
proc interact args {
if {[lindex $args end] eq "leavestep"} {
puts ==>[lindex $args 2]
return
}
puts -nonewline "$args --"
while 1 {
puts -nonewline "> "
flush stdout
gets stdin cmd
if {$cmd eq "c" || $cmd eq ""} break
catch {uplevel 1 $cmd} res
if {[string length $res]} {puts $res}
}
}
proc sreverse str {
set res ""
for {set i [string length $str]} {$i > 0} {} {
append res [string index $str [incr i -1]]
}
set res
}
proc step {name {yesno 1}} {
set mode [expr {$yesno? "add" : "remove"}]
trace $mode execution $name {enterstep leavestep} interact
}
step sreverse
sreverse hello
step sreverse 0
puts [sreverse Goodbye]#-------------------------------------------- gives in a tclsh:
{set res {}} enterstep -->
==>
{for {set i [string length $str]} {$i > 0} {} {
append res [string index $str [incr i -1]]
}} enterstep -->
{string length hello} enterstep -->
==>5
{set i 5} enterstep -->
==>5
{incr i -1} enterstep -->
==>4
{string index hello 4} enterstep -->
==>o
{append res o} enterstep -->
==>o
{incr i -1} enterstep -->
==>3
{string index hello 3} enterstep -->
==>l
{append res l} enterstep -->
==>ol
{incr i -1} enterstep -->
==>2
{string index hello 2} enterstep -->
==>l
{append res l} enterstep -->
==>oll
{incr i -1} enterstep -->
==>1
{string index hello 1} enterstep -->
==>e
{append res e} enterstep -->
==>olle
{incr i -1} enterstep -->
==>0
{string index hello 0} enterstep -->
==>h
{append res h} enterstep -->
==>olleh
==>
{set res} enterstep -->
==>olleh
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