# let.tcl
# Copyright 2001 by Larry Smith
# Wild Open Source, Inc
# For license terms see "COPYING"
#
# let is a replacement for the "set" command. It allows
# multiple assignment, and supports a variety of assignment
# operators:
#
# let a b c = 1 ;# this sets a b and c to 1
# let a b c = 1 + 4 ;# "=" uses expr to process the value to assign
# let a b c += 1 ;# computed assignments allowed, +-*/&| supported
# let a b c := info commands ;# uses eval to process value
# let a b c @= 1 2 3;# "hoisting" assignment, foreach replacement
# let a b c @:= info commands;# uses eval and hoists for assignment
# let a ++ ;# incr and
# let a -- ;# decr are supported.
proc let { args } {
if { [llength $args ] == 2 } {
if [string equal [ lindex $args 1 ] "++" ] {
set result [ uplevel incr [ lindex $args 0 ] ]
} elseif [string equal [ lindex $args 1 ] "--" ] {
set result [ uplevel incr [ lindex $args 0 ] -1 ]
} else {
set result [ uplevel set "$args" ]
}
} else {
regexp {([^=:+\-*/&|@]*)([:+\-*/&|@]?)([@]*)=(.*)} $args -> vars op optional rest
if ![ info exists op ] {
return -code error -errorcode 1 "no valid assignment operator in $args"
}
switch -- $op {
: {
if [llength [info commands [lindex $rest 0]]] {
set result [uplevel $rest]
} else {
set result $rest ;# this should always work...
}
if { "$optional" == "@" } {
set max [ llength $result ]
foreach var $vars res $result {
uplevel 1 [ list set $var $res ]
}
} else {
foreach var $vars {
set result [ uplevel set $var \"$result\" ]
}
}
}
@ {
if { "$optional" == ":" } {
set rest [uplevel $rest]
}
set max [ llength $rest ]
if { $max == 1 } {
eval set rest $rest
set max [ llength $rest ]
}
foreach var $vars res $rest {
set result [ uplevel 1 [ list set $var $res ]]
}
}
+ - - - * - / - & - | {
foreach var $vars {
set result [ uplevel set $var \[ expr \$$var $op ( $rest ) \] ]
}
}
= -
default {
if { [ catch { set result [ uplevel expr $rest ] } ] } {
set result $rest ;# this should always work...
}
foreach var $vars {
set result [ uplevel set $var \"$result\" ]
}
}
}
}
return $result
}DKF - I'd prefer it if stand-alone = was not used, but rather always working with := instead. That's proved to work fairly well. And automagic passing of stuff through eval is not necessary; better to get people to say what they mean IMHO.