if 0 {
Is it possible to assign to a $b ´s value and to b $a ´s value without using a third variable? Is there a function to do so?
Why not just:
let a b @= $b $a
Which, by the way, also allows:
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 are allowed, +-*/&| supported
let a b c := info commands uses eval to process right side
let a b c @= 1 2 3 instead of assigning the list {1 2 3} to a b and c,
it instead assigns the elements in order, resulting
in a getting the value 1, b getting 2 and so on.
let a b c @:= info commands uses eval to get result and uses @= 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}
if 0 {
RS The code fragment (appears twice above)
set i 0
foreach var $vars {
uplevel set $var [ lindex $result $i ]
incr i
}seems like it can be replaced by
foreach var $vars res $result {
uplevel 1 [list set $var $res]
}- if foreach can do a job once, it might as well do it twice ;-) A variable saved, and possibly safer with the list wrapper...
Larry Smith I'd clean forgotten that feature. Yes, it's much more elegant that way. The above code has been corrected. }