CODEWITHSUNDEEP
tcl
Mdr92
Mdr92

Reputation: 29

Move element in list TCL

I have a two problems with my script in TCL language. First: I created list which download values from chart, but i dont know how to move elements in my list, for example:

set list [2,3,4,5,6] # my list

and i want this effect -> 

[1,2,3,4,5] next -> [0,1,2,3,4] etc.

Second: How to create fixed size list for 10 elements? I want 10 elements in my list and when i got > 10 elements i want to remove last element and add new as first element (first problem)

Thanks and sorry for my bad english :)

Upvotes: 0

Views: 928

Answers (1)

Peter Lewerin
Peter Lewerin

Reputation: 13252

To add a new item in the first position in the list, and at the same time limit the list to a given size:

set size 5
set list [list 2 3 4 5 6]
# => 2 3 4 5 6
set list [lrange [linsert $list 0 1] 0 $size-1]
# => 1 2 3 4 5
set list [lrange [linsert $list 0 0] 0 $size-1]
# => 0 1 2 3 4

You can simplify this a bit using a procedure:

proc move {varName new} {
    upvar 1 $varName list
    set size 5
    set list [lrange [linsert $list 0 $new] 0 $size-1]
}

set list [list 2 3 4 5 6]
# => 2 3 4 5 6
move list 1
# => 1 2 3 4 5
move list 0
# => 0 1 2 3 4

Documentation: linsert, list, lrange, proc, set, upvar

Syntax of Tcl index expressions:

  • integer zero-based index number
  • end the last element
  • end-N the nth element before the last element
  • end+N the nth element after the last element (in practice, N should be negative)
  • M-N the nth element before element m
  • M+N the nth element after element m

There can be no whitespace within the expression.

Upvotes: 2

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