Converting A Number List To A Number In CL

I spent a while tonight trying to figure this out, and I didn't find much that helped me, so I thought I would share my solution in case someone else has this problem.

I'm using Common Lisp, and I need to convert a list of numbers into a concatenated version of that number. So I basically need to convert (1 2 3 4) to 1234 (as a number, not a string).

Here's basically what you have to do:

  1. Convert your list into a string
  2. Convert your string into a number

The second part is easy - just use the parse-integer function. However, the first part is what was so tricky to a CL beginner. There isn't a built-in function that I could find to perform that conversion, so I created the following function:

I hope this helps out a few other Common Lisp newbies.