Let's say I have a list {1 2 3 }. I want to unshift it. Create a list which is { 0 1 2 3 }, without creating a new list. This is to save in complexity. In Perl and Ruby, it is possible, by using unshift. Is there a TCL equivalent?
Thanks.
There is no such command in Tcl, but you can easily make it yourself:
proc lunshift {var args} {
upvar 1 $var list
set list [linsert $list[set list {}] 0 {*}$args]
}
The [set list {}] part is a trick to make the list unshared, so no duplicate will be made. See the Tcl wiki for details.
Demo:
set mylist {1 2 3}
lunshift mylist 0
puts $mylist; # Result => 0 1 2 3