PYK 2015-11-08: procstep is a drop-in replacement for proc that evaluates one command of a procedure body at at time, and a hook to inspect and manipulate the command before it is evaluated, and another to react to return conditions of the evaluation.
rename proc ::tcl::proc
::tcl::proc proc {name args body} {
::uplevel [::list ::tcl::proc $name $args [::list apply [::list args [
::string map [::list {${body}} [::list $body]] {
::foreach command [::scriptSplit ${body}] {
::if {[::catch [::list ::uplevel 1 [
::cmdhandler $command]] cres copts]} {
::tailcall ::errorhandler $cres $copts
}
}
}
]] [uplevel {namespace current}]]]
}
::tcl::proc cmdhandler command {
::puts stderr [::list {now executing} $command]
return $command
}
::tcl::proc errorhandler {cres copts} {
::puts stderr [list {got an error} $cres]
#puts [uplevel info locals]
}Here is variant that improves runtime performance quite a bit by rewriting the body when the procedure is created. This leaves no place to put the result variables of the catch, so they get stuffed into ::tcl namespace instead:
::tcl::proc proc {name args body} {
set newbody {}
::foreach command [::scriptSplit $body] {
::append newbody [::string map [::list {${command}} [::list $command]] {
::if {[::catch {if 1 [
::cmdhandler ${command}]} ::tcl::cres ::tcl::copts]} {
::errorhandler $::tcl::cres $::tcl::copts
}
}]
}
::uplevel [::list ::tcl::proc $name $args $newbody]
}