"Bill Page" <[EMAIL PROTECTED]> writes:
| On November 20, 2005 11:50 PM Gaby wrote:
| > |
| > | We have mentioned before on this list the very good article
| > |
| > | http://en.wikipedia.org/wiki/Datatype
| > |
| > | about type systems in programming languages. "strong type
| > | checking" has several different definitions but I think most
| > | people would agree that Lisp is a strong dynamically typed
| > | language by most of these definitions.
| >
| > That is interesting but the link above is confused to start with.
| > I quote:
| >
| > An example of the absence of strong typing is a C cast
| > gone wrong; if you cast a value in C, not only is the
| > compiler required to allow the code, but the runtime is
| > expected to allow it as well.
| >
| > That is misleading at best. The core C system is consistent
| > -- the only trouble is that I would be in difficult position
| > to prove it, in the mathematical sense because I have not sense
| > any formal definition of C in the mathematical sense. However,
| > the fundamental point is that if you make a cast, the runtime is
| > not required to accept it if it is semantically ill-formed. And
| > the compiler is not required to accept it if it can somehow
| > determine that it is invalid. In fact, we're seeing more
| > compilers taking advantages of those semantics invariants, in
| > terms of optimizations.
| >
|
| I think you are wrong.
No -- sorry, Bill you can't have it right on this one.
| For example consider this example:
|
| /*
| 'caste' example of weak typing in C
| Author: Bill Page
| Date: 21 Nov 2005
| */
| #include <stdio.h>
| int main(int argn, char *argv[]) {
| float j;
|
| (int)j = 1;
| printf("float: %d\n",j);
| return 0;
| }
|
| ------
|
| You can compile this with gcc without errors and it runs without
| error. What result would you expect it to return?
Your program is ill-formed according to ISO C rules and semantics and
my compiler rightly rejects it:
merlin[12:54]% cat bill-page.c && gcc bill-page.c
/*
'caste' example of weak typing in C
Author: Bill Page
Date: 21 Nov 2005
*/
#include <stdio.h>
int main(int argn, char *argv[]) {
float j;
(int)j = 1;
printf("float: %d\n",j);
return 0;
}
bill-page.c: In function 'main':
bill-page.c:10: error: invalid lvalue in assignment
| I still think the referenced article is well balanced and
| accurate.
I don't think so If is full of confusion and misunderstanding.
Unfortunately, many people take it as a Bible sentence don't go and do
a minimum scrutinity as would be required in a scientific setting :-(
-- Gaby
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