Question

I wanted to create a list of numbers with missing numbers in a given list as provided in the example below

Existing list { 1,3, 5, 9 , 13, 15}

Resultant list { 2,4,6,7,8,10,11,12,14}

Answer 1

Extended TCL has the function intersect3 which as one of its return values gives a list of A-B. You could intersect your list with a list of all possible numbers that span your list.

If you don’t use Extended TCL, you’ll have to implement something yourself.

I hardly ever use TCL, so maybe there’s a better way, but the basic approach is to just sort the list, then run through it and find the missing values:

#!/usr/bin/tclsh

set A {1 3 5 9 13 15}

set A [lsort -integer $A]
set B {}
set x 0
set y [lindex $A $x]

while {$x < [llength $A]} {
    set i [lindex $A $x]
    while {$y < $i} {
        lappend B $y
        incr y
    }
    incr x
    incr y
}
puts $B

Output:

2 4 6 7 8 10 11 12 14