automatic type conversion for comparison operators

[Russ]

I posted a message on this several days ago, but it apparently got
lost
in googlespace, so I'll try it again.

I recently discovered a bug in my code that apparently resulted from
the automatic conversion of a function pointer to an integer.

Say you have a class member function called getCount(), which
returns an integer. Now suppose you write something like

if obj.getCount < 3: ...

This is an error because the parentheses were left off. But Python
somehow compares the function pointer with an integer without
complaining. Unless there is a darn good reason for allowing
comparisons of this type (and I can't think of one), I think
Python should flag this as an Exception.

 

[Dan Bishop]

I posted a message on this several days ago, but it apparently got
lost
in googlespace, so I'll try it again.

I recently discovered a bug in my code that apparently resulted from
the automatic conversion of a function pointer to an integer.

Say you have a class member function called getCount(), which
returns an integer. Now suppose you write something like

if obj.getCount < 3: ...

This is an error because the parentheses were left off.

BTW, are you a former Pascal programmer?

But Python
somehow compares the function pointer with an integer without
complaining. Unless there is a darn good reason for allowing
comparisons of this type (and I can't think of one), I think
Python should flag this as an Exception.

IIRC, the reason is for backwards compatibility with a long-obsolete
version of Python in which it wasn't possible for __cmp__ to throw an
exception. That's not darn good, so this behavior is already slated
for removal in version 3.0.

 

[Russ]

BTW, are you a former Pascal programmer?

No. Why do you ask? [The code snippet I wrote was made up to get a
point across. I
did not actually use that function name in my code.]

IIRC, the reason is for backwards compatibility with a long-obsolete
version of Python in which it wasn't possible for __cmp__ to throw an
exception. That's not darn good, so this behavior is already slated
for removal in version 3.0.

That's good to know. Thanks.

 

[Dan Bishop]

BTW, are you a former Pascal programmer?

No. Why do you ask? [The code snippet I wrote was made up to get a
point across. I
did not actually use that function name in my code.]

I just have a hypothesis that former Pascal/Basic programmers are much
more likely than C/C++/Java programmers to forget the () on a function
call. Nothing to do with the (Java-like) function name.