From: Jim Weirich <jweirich@...>
Date: 2003-02-16T15:14:02+09:00
Subject: Re: von Rossum on Strong vs. Weak Typing

On Sat, 2003-02-15 at 23:44, Paul Brannan wrote:
> On Sat, Feb 15, 2003 at 02:35:08PM +0900, Ryan Pavlik wrote:
> > Consider that a char is just 1 byte, and while there's pretty syntax:
> > 
> >     char a = 'A'
> > 
> > there's no difference between that and
> > 
> >     char a = 65
> 
> Both 'A' and 65 are literals with type int.  You haven't shown that C is
> typeless; only that 'A' and 65 have the same type, and that this type
> can be implicitly converted to a char.
> 
> > Bringing this back on topic, C is statically typed, which gives the
> > compiler the ability to do some nice optimizations, but results in
> > weaker typing, too (at least by matz's definition).
> 
> Static typing does not result in weak typing.  C++, Java, and OCaml are
> examples of languages that have strong static typing.  C's weak typing
> is the result of being able to implicitly convert from almost any type
> to almost any other type (or as matz says, the type "can be mixed and
> changed very easily").

Actually, I would say C is weakly typed because it is easy to accidently
interpret data as the wrong type ... especially in pre-ANSI C (without
prototypes).  

For example ...

One file contains ...

   extern int f();
   int main () {
      f(3.1416);
   }

In another file ...

   int f(x)
   int x;
   {
      ...
   }

Unions are also problematic, although in that case you expect problems
so accidents are less likely.   

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)