Here comes the code for the extension to [subst] introduced in [extending the notation of proc args]...
The documentation is written in [tcldoc].
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# 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 -inplace
, then false
is returned
# if any call to ::subst
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 true
or false
is returned
# @param -- optionally used to separate switches from other parameters
# @param args forwards all args
defined for ::subst
,
# 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 [lrange $args 0 end-1] -nocomplain]] != -1} {
uplevel subst_nocomplain [lreplace $args $i $i]
} else {
uplevel tcl_subst $args
}
}
======
e.g.
======
% set v1 hello
% set v2 world
% subst -nocomplain {$v1 $v2 $v3}
hello world $v3
======
I find this useful in code-generation / template expansion situations.
The following further modification handles unknown commands.
However, I'm not quite happy with the way this works. It relies on `regexp` match of the human-readable "invalid command name" message (it seems there is no -errorcode for this error).
Also, just escaping the `[` works for trivial situations, but can have unexpected results in some cases. See example below...
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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
} on error {msg info} {
if {[regexp {invalid command name "(.*)"} $msg - cmd]} {
regsub -all [cat {\[ *} $cmd] $args {\\\0} args
uplevel subst_nocomplain $args
} else {
return -code error -options $info
}
}
}
proc cat {args} {join $args ""}
======
e.g.
======
proc bar {args} {
string toupper $args
}
set v1 hello
set v2 world
puts [subst -nocomplain {$v1 [foo $v2] [foo [bar a b c]] $v3}]
hello [foo world] [foo A B C] $v3
puts [subst -nocomplain {$v1 [bar [foo $v2] xx] [foo [bar a b c]] $v3}]
hello {[FOO} WORLD xx] [foo A B C] $v3
======
[AMG]: Bug reported [http://core.tcl.tk/tcl/tktview/311e61d12ad1eb6355c13d2d2ed4acf1c45c4557], thanks!
[AMG]: Why are you modifying the entire $args list? Only the last element contains the string to be [subst]'ed. ''-- samoc: true, and my first implementation split "args" into "options" and "string", however the code far smaller this way (and there is no risk that any of the legal subset options contains a `$` that would be changed by `string map`).''
[AMG]: Here are some more cases that don't work:
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subst -nocomplain {[ foo ]}
subst -nocomplain {[expr 42; foo]}
subst -nocomplain {[if {1} {foo}]}
======
Things can get arbitrarily fancy here. I'm not sure what exactly you want each of the above examples to return. ''-- samoc: the space after `[[` is fixed now, thats handy for generating bash scripts, see below...''
I'm puzzled about where the close bracket went following WORLD in your last example, or why xx isn't capitalised. ''-- samoc: `[[foo` becomes `{[[foo}`. Then, what was "foo's" close bracket gets eaten up by `bar`. i.e. `[bar {[[foo} world]`. So the xx is not passed to `bar`.
----
another example:
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set user sam
proc get_user_name {args} {return "Sam O'C"}
set script [subst -nocomplain \
{#!/bin/bash
file=$1
if [ -f $user/$file ]
then
echo "User [get_user_name $user] can't find: $file"
fi
}]
puts $script
#!/bin/bash
file=$1
if [ -f sam/$file ]
then
echo "User Sam O'C can't find: $file"
fi
======
<>String Processing