Problem Statement

Provide a function or mechanism to convert a provided string into URL encoding representation. In URL encoding, special characters, control characters and extended characters are converted into a percent symbol followed by a two digit hexadecimal code, So a space character encodes into %20 within the string. For the purposes of this task, every character except 0-9, A-Z and a-z requires conversion, so the following characters all require conversion by default:

The string "http://foo bar/" would be encoded as "http%3A%2F%2Ffoo%20bar%2F".

It is permissible to use an exception string (containing a set of symbols that do not need to be converted). However, this is an optional feature and is not a requirement of this task.

Let's start with the solution:

(de urlEncodeTooMuch (Str)
   (pack
      (mapcar
         '((C)
            (if (or (>= "9" C "0") (>= "Z" (uppc C) "A"))
               C
               (list '% (hex (char C))) ) )
         (chop Str) ) ) )