Adding a nested element to a "flat" list

Question

I have a "flat" Tcl list. Now I want to append a new element as a child to one of the existing elements. How can I do this?

This is what I tried:

[ lindex $flights $i ] [ lindex $flight 0 ] ]

I try to add an element form the list "flight" to an element of the list "flights". The element $i in the flights list already exists.

I might be running against Tcl syntax as I'm new to Tcl.

Thanks for your help.

TrojanName · Accepted Answer · 2012-06-17 16:11:20Z

2

You can use lset to replace an element of your list with a new list. http://www.tcl.tk/man/tcl8.5/TclCmd/lset.htm The first element of the new list will be the old element, the 2nd element will be its child. Here's an example:

% set flights [list a b c d e]
a b c d e
% set i 1
1
% lset flights $i [list b child]
a {b child} c d e
% lindex $flights 1
b child
% lindex [lindex $flights 1] 1
child
% lindex [lindex $flights 1] 0
b

edited Jun 17, 2012 at 16:11

answered Jun 17, 2012 at 14:50

TrojanName

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2 Comments

Donal Fellows Over a year ago

Also: lindex $flights 1 0 is useful, and in 8.6 you can use lset flights $i end+1 child. (Doesn't work in 8.5, which won't let lset extend lists.)

Paul Over a year ago

Thanks, I missed the list keyword.

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