undef or zero? (semantic question)

[John]

Hi all,


I have been thinking about how to define a value. That's the idea.


If you have one String, you can get the length of the String. But what
happens if there is no String??? you would say:

$string_length = undef;

or

$string_length = 0;

to me the value should be undefined but zero can play the same role.

How do you think this should be addressed?


Thanks for your comments
J

 

[fifo]

If you have one String, you can get the length of the String. But what
happens if there is no String??? you would say:

$string_length = undef;

or

$string_length = 0;

to me the value should be undefined but zero can play the same role.

How do you think this should be addressed?

Well

$ perl -le'print length(undef)'
0

which I suppose is indeed the number of characters in an undefined
value. If you're writing your own String_length function, it could
return 0 or undef (each with or without an accompanying warning) or it
could throw an exception. What you choose depends on how you intend to
use it.

 

[ko]

Hi all,

I have been thinking about how to define a value. That's the idea.

A simple assignment will do, anything except undef.

If you have one String, you can get the length of the String. But what
happens if there is no String??? you would say:

$string_length = undef;

or

$string_length = 0;

They are not the same. First, try the length() function to verify that
the lengths are different. Second, try the defined() function to verify
that assignment of 0 results in a defined value.

to me the value should be undefined but zero can play the same role.

How do you think this should be addressed?

Start with:

perldoc -f defined
perldoc perlsyn ('Declarations' and 'Truth and Falsehood' sections)

Thanks for your comments
J

HTH -keith

 

[Brad Baxter]

If you have one String, you can get the length of the String. But what

happens if there is no String??? you would say:

$string_length = undef;

or

$string_length = 0;

to me the value should be undefined but zero can play the same role.

Perhaps:

$string_length = defined $string ? length $string : undef;

Then the definedness of $string_length would parallel that of $string.

Regards,

Brad