TCL: for loop with multiple variables

TCL for loop is in the form of
for { init } { test } { next } { body }
. The examples below shows for loops with more than one variables:

1. Example 1:

   for { set i 0; set j 10 } { $i < $j } { incr i; incr j -1 } {
      puts "$i $j"
   }
   

   Output:

   0 10
   1 9
   2 8
   3 7
   4 6
   

2. Example 2:

   for { set i 0; set j 10 } { $i < 3 && $j < 7 } { incr i; incr j -1 } {
      puts "$i $j"
   }
   

   Output:

   0 10
   1 9
   2 8