Re: [Xotcl] Troubles with upvar and the trace mechanism from the tutorial.

From: Gustaf Neumann <neumann_at_wu-wien.ac.at>
Date: Sun, 19 Nov 2006 22:02:40 +0100

Ramam,

you should change "upvar" to "my upvar" as in the following method

X instproc bar {ar args} {
  puts "bar"
  my upvar $ar arr
  puts "upvard"
  barray arr
}

otherwise you will upvar to the filter. The plain tcl upvar is not
very useful, when interceptors are added/removed dynamically.

Therefore, xotcl provides the methods "upvar" and "uplevel"
to achieve interceptor transparency. This means that an upvar/uplevel
refers always to the last non-interceptor method (skipping
filters and mixins).

best regards
-gustaf neumann



Shishir Ramam schrieb:
>
> I am passing an array name by reference across an instproc.
>
> The vanilla version works just fine (see creation of x1 midway through
> the code segment).
>
> To add some debugging in, I essentially used the trace example from
> the tutorial, and funnily,
> the upvar stopped doing it's job (see error on creating x2 towards the
> end of the code segment).
>
> To get rudimentary debug control of the parray proc, I copied it into
> a proc called barray. None of the logic is changed -
> just my crude attempt at adding breadcrumbs.
>
> I have included the output at the end of the code segment.
>
> Running Windows XP Pro + Active Tcl 8.4.13 + XoTcl 1.4.0.
>
> thanks for all help.
> -shishir
>
> <CODE SEGMENT>
> package require XOTcl
> namespace import ::xotcl::*
>
>
> proc barray {a {pattern "*"}} {
> puts "barray"
> upvar 1 $a arr
> if {![array exists arr]} {
> error "\"$a\" isn't an array"
> }
> set maxl 0
> foreach name [lsort [array names arr $pattern]] {
> if {[string length $name] > $maxl} {
> set maxl [string length $name]
> }
> }
> set maxl [expr {$maxl + [string length $a] + 2}]
> foreach name [lsort [array names arr $pattern]] {
> set nameString [format %s(%s) $a $name]
> puts stdout [format "%-*s = %s" $maxl $nameString $arr($name)]
> }
> }
>
> Class X
>
> X instproc bar {ar args} {
> puts "bar"
> upvar $ar arr
> puts "upvard"
> barray arr
> }
>
>
>
> X instproc init {args} {
> array set arr {a 1 b 2}
> parray arr
> my bar arr
> }
>
> X x1
>
>
> Object Trace
> Trace set traceStream stdout
> Trace proc openTraceFile name {
> my set traceStream [open $name w]
> }
> Trace proc closeTraceFile {} {
> close $Trace::traceStream
> my set traceStream stdout
> }
> Trace proc puts line {
> puts $Trace::traceStream $line
> }
> Trace proc add className {
> $className instfilter [concat [$className info filter] traceFilter]
> }
>
> Object instproc traceFilter args {
> # don't trace the Trace object
> if {[string equal [self] ::Trace]} {return [next]}
> set context "[self class]->[self callingproc]"
> set method [self calledproc]
> switch -- $method {
> proc -
> instproc {::set dargs [list [lindex $args 0] [lindex $args 1] ...] }
> default {::set dargs $args }
> }
> Trace::puts "CALL $context> [self]->$method $dargs"
> set result [next]
> Trace::puts "EXIT $context> [self]->$method ($result)"
> return $result
> }
>
> Trace add X
>
> X x2
>
> </CODE SEGMENT>
>
> ------------
>
> <OUTPUT>
> arr(a) = 1
> arr(b) = 2
> bar
> upvard
> barray
> arr(a) = 1
> arr(b) = 2
> CALL ::xotcl::Object->> ::x2->cleanup
> EXIT ::xotcl::Object->> ::x2->cleanup ()
> CALL ::xotcl::Object->> ::x2->configure
> EXIT ::xotcl::Object->> ::x2->configure (0)
> CALL ::xotcl::Object->> ::x2->init
> arr(a) = 1
> arr(b) = 2
> CALL ::xotcl::Object->init> ::x2->bar arr
> bar
> upvard
> barray
> "arr" isn't an array
> </OUTPUT>
>
> ----
>
> <ERRORINFO>
> % set errorInfo
> "arr" isn't an array
> while executing
> "error "\"$a\" isn't an array""
> (procedure "barray" line 5)
> invoked from within
> "barray arr"
> (procedure "bar" line 6)
> invoked from within
> "next"
> (procedure "bar" line 13)
> ::x2 ::xotcl::Object->traceFilter
> invoked from within
> "my bar arr"
> (procedure "init" line 5)
> invoked from within
> "next"
> (procedure "init" line 13)
> ::x2 ::xotcl::Object->traceFilter
> ::X ::xotcl::Class->recreate
> ::X ::xotcl::Class->create
> ::X ::xotcl::Class->unknown
> invoked from within
> "X x2"
> (file "c:/temp/trace_trouble.tcl" line 81)
> invoked from within
> "source c:/temp/trace_trouble.tcl"
> </ERRORINFO>
>
>
> ------------------------------------------------------------------------
>
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