Problem Statement

Show a nested loop which searches a two-dimensional array filled with random numbers uniformly distributed over

[ 1 , … , 20 ]

{\displaystyle [1,\ldots ,20]}

. The loops iterate rows and columns of the array printing the elements until the value

20

{\displaystyle 20}

is met. Specifically, this task also shows how to break out of nested loops.

Let's start with the solution:

set ary [subst [lrepeat 10 [lrepeat 5 {[expr int(rand()*20+1)]}]]]

try {
    foreach row $ary {
        foreach col $row {
            puts -nonewline [format %3s $col]
            if {$col == 20} {
                throw MULTIBREAK "we're done"
            }
        }
        puts ,
    }
} trap MULTIBREAK {} {}
puts " done"