I remember in some intro-level compsci class learning that credit card numbers were checksummed, and writing basic functions to validate those checksums as an exercize. I was young and was still using my "starter" credit card with a whopping limit of $500, so that was all news to me.

Alex's company had a problem processing credit cards: they rejected a lot of credit cards as being invalid. The checksum code seemed to be working fine, so what could the problem be? Well, the problem became more obvious when someone's card worked one day, and stopped working the very next day, and they just so happened to be the first and last day of the month.

We previously discussed some whitespacing choices in a C++ codebase. Tim promised that there were more WTFs lurking in there, and has delivered one.

Let's start with this class constructor:

As oft stated, the "right" way to validate emails is to do a bare minimum sanity check on format, and then send a verification message to the email address the user supplied; it's the only way to ensure that what they gave you isn't just syntactically valid, but is actually usable.

But even that simple approach leaves places to go wrong. Take a look at this code, from Lana.

Markus does QA, and this means writing automated tests which wrap around the code written by developers. Mostly this is a "black box" situation, where Markus doesn't look at the code, and instead goes by the interface and the requirements. Sometimes, though, he does look at the code, and wishes he hadn't.

Today's snippet comes from a program which is meant to generate PDF files and then, optionally, email them. There are a few methods we're going to look at, because they invested a surprising amount of code into doing this the wrong way.

Today, we look at a simple bit of bad code. The badness is not that they're using Oracle, though that's always bad. But it's how they're writing this PL/SQL stored function:

  FUNCTION CONVERT_STRING_TO_DATE --Public
    (p_date_string IN Varchar2,
       p_date_format IN Varchar2 DEFAULT c_date_format)
    Return Date

   AS

   BEGIN

    If p_date_string Is Null Then
        Return Null;
      Else
        Return To_Date(p_date_string, p_date_format);
      End If;

   END;  -- FUNCTION CONVERT_STRING_DATE