Bob Martin’s eliminate boolean arguments tip – an example

I don’t always agree with Bob Martin’s Clean Code Tip #12: Eliminate Boolean Arguments – probably because the mathematician in me believes that there are such things as functions of a boolean value – but I came across an example in a WinForms app today where I’d apply it.

void FindApplicant(int id)
{
    processUIChange(true);
    applicant= getTheApplicantFromDataLayer(id);
    processUIChange(false);
}

turned out to mean:

void ProcessUI(bool processing)
{
    if(processing)
    {
      this.Enabled=false;  
    }
    else
    {
       ... do a whole load of stuff
    }
}

which would have been easier to read as:

void FindApplicant(int id)
{
    DisableUIWhileUpdating();
    applicant= getTheApplicantFromDataLayer(id);
    UpdateUIAfterDataChange();
}

void DisableUIWhileUpdating()
{
    this.Enabled=false
}
void UpdateUIafterDataChange()
{
    ...do a whole load of stuff
}

Highly Unlikely — The Mark of the Beast Bug

In 1991, amongst a series of theorems about rounding in floating point arithmetic calculations, the author parenthetically noted that rounding a number to 53 significant digits, and then rounding it again to 52 significant digits, might produce a different answer compared to when you do the rounding to 52 digits all in one go. He all but apologised for the parenthesis, noting it was “highly unlikely to affect any practical program adversely.”

19 years and 10 months later a researcher discovered that the “Mark of the Beast Bug” could freeze almost any computer in the world, and that millions of webservers could be taken down by it almost at the touch of a button — because of an error when rounding a very very small number, first to 53 significant digits, and then to 52.