Here comes the code for the extension to subst introduced in extending the notation of proc args...
The documentation is written in tcldoc.
# provides a fail-safe {@link http://www.tcl.tk/man/tcl8.5/TclCmd/subst.htm
# http://www.tcl.tk/man/tcl8.5/TclCmd/subst.htm} which optionally performs
# substitutions in an uplevel. If <code>-inplace</code>, then <code>false</code> is returned
# if any call to <code>::subst</code> fails. All variables are handled anyways.
# @param -nocomplain in case of an error, the initial value is returned and no error is thrown
# @param -uplevel the level at which substitutions are performed. Defaults to the current context
# @param -inplace all non-switch arguments at the end are variable names in the caller's context.
# Their value is replaced and <code>true</code> or <code>false</code> is returned
# @param -- optionally used to separate switches from other parameters
# @param args forwards all <code>args</code> defined for <code>::subst</code>,
# but allows multiple strings or variable names
# @return the value of the last argument after performing TCL substitutions
# @see http://www.tcl.tk/man/tcl8.5/TclCmd/uplevel.htm
# http://www.tcl.tk/man/tcl8.5/TclCmd/uplevel.htm
proc subst {args} {
set level 0
set complain true
set inplace false
set switches {}
for {set i 0} {$i < 7} {incr i} {
set c [lindex $args $i]
switch $c {
-uplevel {set level [lindex $args [incr i]]}
-nocomplain {set complain false}
-inplace {set inplace true}
-nobackslashes - -nocommands - -novariables {lappend switches $c}
default {
if {$c eq {--}} {incr i}
break
}
}
}
set args [lrange $args $i end]
catch {incr level}
# 4 paths for -nocomplain and -inplace
if {$inplace} {
set ret true
foreach args $args {
upvar $args myvar
if {[catch {uplevel $level [list ::subst $myvar]} result options]} {
if {$complain} {
return {*}$options $result
} else {
# TODO: log error?
set ret false
}
} else {
set myvar $result
}
}
} else {
set ret {}
foreach args $args {
if {[catch {uplevel $level [list ::subst $args]} result options]} {
if {$complain} {
return {*}$options $result
} else {
# TODO: log error?
lappend ret $args
}
} else {
lappend ret $result
}
}
}
return $ret
}For redirection see: Overloading Proc
---
samoc 20140612: Here is another subst replacement that adds a -nocomplain option to ignore unknown variable names.
rename subst tcl_subst
proc subst_nocomplain {args} {
try {
uplevel tcl_subst $args
} trap {TCL LOOKUP VARNAME} {msg info} {
lassign [dict get $info -errorcode] - - - var
set args [string map [list \$$var \\\$$var] $args]
uplevel subst_nocomplain $args
}
}
proc subst {args} {
if {[set i [lsearch $args -nocomplain]] != -1} {
uplevel subst_nocomplain [lreplace $args $i $i]
} else {
uplevel tcl_subst $args
}
}e.g.
set v1 hello
set v2 world
puts [subst -nocomplain {$v1 $v2 $v3}
hello world $v3I find this useful in code-generation / template expansion situations.