Phone Number Validation Function

[Bob Sneidar]

Hi all. 

Since I needed to write one, I thought I would share this phone number validation function. NOTE: it only works for phone numbers of the following format:

-- pure numbers
nnnnnnn
nnnnnnnnnn

-- formatted numbers
nnn-nnnn
nnn-nnn-nnnn
(nnn) nnn-nnnn

It will also accept a space delimited extension so long as it begins with x, ex or ext. 

Anyone who wants to massage it into shape for European or other phone number formats can do so. The range checking is somewhat coarse, because I had difficulty determining what the lowest and highest area code and prefix can be, and also it may change in the future. Enjoy! 

Bob S

function isPhoneNum pValue
   /*
   A phone number is a value whose raw numeric value is between 1000000 and 9999999, or 1000000000 and 
   9999999999, with an optional numeric value delimited by a space. Additionally, the first and fifth characters
   can be ( and ) respectively, in which case the 6th character must be a space and the tenth character must be 
   a dash. 
   */
   put pValue into tPhoneNumber -- preserve initial value
   put last word of tPhoneNumber into tExtension
   
   if first char of tExtension is "x" or char 1 to 3 of tExtension is "ext" then 
      delete last word of tPhoneNumber -- lose the extension
   else 
      put empty into tExtension -- it's not a valid extension
   end if
   
   -- range check
   put cleanAscii(tPhoneNumber, "numbers") into tPhnValue
   
   if tPhnValue > 9999999 then
      if tPhnValue < 1000000000 or tPhnValue > 9999999999 then
         return false
      end if
   else
      if tPhnValue < 1000000 then
         return false
      end if
   end if
   
   -- pure numbers are OK
   if tPhoneNumber = tPhnValue then return true
   
   -- allowed characters
   if length(tPhnValue) = 7 then
      -- length must be 8 chars and char 4 must be a dash
      if length(tPhoneNumber) <> 8 or char 4 of tPhoneNumber is not "-" then
         return false
      end if
   else
      -- length must be 14, 1st char must be (, 5th char must be ), 6th char must be space and 10th char must be -
      -- or else length must be 12, 4th char must be - and 8th char must be -
      if length(tPhoneNumber) <> 14 or length(tPhoneNumber) <> 12 then 
         return false
      end if
      
      if length(tPhoneNumber) is 14 then
         if char 1 of tPhoneNumber is not "(" or \
               char 5 of tPhoneNumber is not ")" or \
               char 6 of tPhoneNumber is not space or \
               char 10 of tPhoneNumber is not "-" then 
            return false
         end if
      else
         if char 4 of tPhoneNumber is not "-" or \
               char 8 of tPhoneNumber is not "-" then 
            return false
         end if
      end if
   end if
   return true
end isPhoneNum