Thomas (boggyb) wrote,

Today's discovery is that Perl doesn't have a null value. In the following code, the if statement will throw an error:

undef $foo;
if ($foo == 2)
    # do something

This is because Perl doesn't actually have a concept of null. The nearest thing is an undefined variable (undefined in the sense that the variable does not exist, not in the sense that the variable exists with unknown contents), except you can't directly use it with comparisions or logical operators. I like VB, as it does have such a thing:

Dim Foo
Foo = Null
If Foo = 2 Then
    # do something
End If

In VB, Null is a distinct value from zero (the classical C representation), and does pretty much what you expect. There are also distinct values for Nothing (an object variable that does not refer to an actual object, like a C null pointer but with error handling), and Empty (an optional parameter that was not provided). 'Course, to use these you do need to use Variants which have a performance hit, but it's not really significant anymore in this age of multi-gigahertz processors and it makes database work nice.

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