Questions about app design - OOP with python classes

[John Nagle]

Steven D'Aprano wrote:
> On Fri, 02 Mar 2007 09:30:20 +0100, Diez B. Roggisch wrote:
> 
> 
>>>A type system doesn't help. So what if they're both floats? The test
>>>is still bogus, your code will still wait too long to engage the
>>>retro-rockets, and the billion dollar space craft will still be travelling
>>>at hundreds of miles an hour when it reaches the surface of Mars.
>>
>>A type system _could_ help. 
> 
> 
> It's easy to wave your hands and say that Microsoft could have done
> something different, but they had to work with what they had, not some
> hypothetical alternative language with a hypothetical type system that
> didn't exist then (if it even exists now).

     The Pascal/Ada/Modula family of languages all had type systems
with restrictions on conversion.  Unlike C, types in Pascal
are not simply abbreviations of the type; they're unique types.

     This turns out to be too restrictive, but it's certainly been
tried.

     There are C++ class libraries that understand units.  And
the conversion factors can be dealt with at compile time, so
the overhead goes away.

				John Nagle