[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: 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 uplevel 1 [list catch $cmd res] uplevel 1 { 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 eybdooG ---- [Category Debugging] - [Arts and crafts of Tcl-Tk programming]