My gmail send out with line wrap...
so some lines are true one line source code but wrapped.
The (http:// .... ) normally is part of previous line.
Same as (0..4).each  ... etc is wrapped.

I do not do more error checking.
so any character not /\d/ will simply replace by zero.

of course, you could add parameter checking as you like like, for example

raise "number invalid" if number !~ /^\d+$/

Have Fun.