[Python-3000] Type Comparisons with Godel Numbers

[Talin]

Greg Ewing <greg.ewing <at> canterbury.ac.nz> writes:

> Giovanni Bajo wrote:
> 
> > Another (similar) way would be to let the user pay for the high typechecking
> > price in normal cases *but* provide a list[int] class, which is a list
> > decorated with typechecks on modification operations. We could have
> > list[int|float]() to construct a list which can hold either ints or floats.
> 
> This is worth thinking about. Recently when pondering the
> question of when it would or would not be appropriate to
> put in type assertions to help catch bugs, I concluded
> that it makes the most sense to do so when building a
> data structure, but not when just passing things around
> between calls.

This makes total sense to me. You don't check the type of each
entry of the list - you check the type of the list itself. This is
pretty much the way statically typed languages work.

This means that you can't pass a regular list to a function
that expects a "list of ints". So its an extra step to convert
the list to the proper type. As long as the syntax isn't too
hard to type, that shouldn't be a problem, and this way the
user knows that they are paying the cost for the conversion.
"Explicit is better than implicit".

-- Talin