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Python from Wise Guy's Viewpoint

Marshall Spight mspight at dnai.com
Fri Oct 24 17:12:18 EDT 2003 
"Pascal Costanza" <costanza at web.de> wrote in message news:bnarks$v7k$1 at f1node01.rhrz.uni-bonn.de...
>
> >>>For one thing, type declarations *cannot* become out-of-date (as
> >>>comments can and often do) because a discrepancy between type
> >>>declaration and definition will be immidiately flagged by the compiler.
> >>
> >>They same holds for assertions as soon as they are run by the test suite.
> >
> > That is not true unless your test suite is bit-wise exhaustive.
>
> Assertions cannot become out-of-date. If an assertion doesn't hold
> anymore, it will be flagged by the test suite.

This is only correct if all assertions receive coverage from the
test suite, which requires significant discipline, manual testcase
writing,  and recurring manual verification, and even then,
it is only true at runtime. And assertions only verify what
you manually specify.

The benefits of a type system require significantly less manual
work, and find errors at compile time. Also, they verify that
type errors provable do not occur anywhere in the program,
vs. just where you manually specify.


Marshall
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