Question

I am trying to delete every character from the beginning of my string, that is not an Alpha-character.

However, when there are only non-alpha characters (like “!!” or “?!?”) in the string, it spits out an Access Violation!

Here is my code:

  // The Log(); is a routine that adds stuff to my log memo.
  Log('Begin Parse');
  while not IsLetter(ParsedName[1]) do
   begin
     Log('Checking Length - Length is '+IntToStr(Length(ParsedName))+' ...');
     if Length(ParsedName) <> 0 then
     Begin
     Log('Deleting Char ...');
     Delete(ParsedName,1,1);
     Log('Deleted Char ...');
     End;
     Log('Checking Length - Length is now '+IntToStr(Length(ParsedName))+' ...');
   end;
   // It never reaches this point!
   Log('End Parse');

This is what my log produces:

21:51:19: Checking Length - Length is 2 ...
21:51:19: Deleting Char ...
21:51:19: Deleted Char ...
21:51:19: Checking Length - Length is now 1 ...
21:51:19: Checking Length - Length is 1 ...
21:51:19: Deleting Char ...
21:51:19: Deleted Char ...
21:51:19: Checking Length - Length is now 0 ...
21:51:19: Access violation at address 007A1C09 in module 'Project1.exe'. Read of address 00000000 

As you see, it happens right after all the chars have been deleted. I assume the problem lies that somehow, I am trying to access something that is not there, but how I am doing that, I cannot see.

EDIT: Yes, I know it’s a stupid question and all that stuff – I just oversaw something. Don’t tell me that doesen’t ever happen to you 😉

Answer 1

This question has nothing to do with Delete. Delete works even if you tell it to delete characters that do not exist.

The line

while not IsLetter(ParsedName[1]) do

tries to access ParsedName[1], so this character has better to exist. Your code isn’t particularly beautiful, but a simple workaround is

while (length(ParsedName) > 0) and not IsLetter(ParsedName[1]) do

You can do just

while (length(ParsedName) > 0) and not IsLetter(ParsedName[1]) do
  Delete(ParsedName, 1, 1);