Function Definition Example
===========================

   Here is an example of a user-defined function, called `myprint', that
takes a number and prints it in a specific format.

     function myprint(num)
     {
          printf "%6.3g\n", num
     }

To illustrate, here is an `awk' rule which uses our `myprint' function:

     $3 > 0     { myprint($3) }

This program prints, in our special format, all the third fields that
contain a positive number in our input.  Therefore, when given:

      1.2   3.4    5.6   7.8
      9.10 11.12 -13.14 15.16
     17.18 19.20  21.22 23.24

this program, using our function to format the results, prints:

        5.6
       21.2

   Here is a rather contrived example of a recursive function.  It
prints a string backwards:

     function rev (str, len) {
         if (len == 0) {
             printf "\n"
             return
         }
         printf "%c", substr(str, len, 1)
         rev(str, len - 1)
     }