Pointers with C- a query

[s.subbarayan]

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows java
able to do this with out pointers?
I jus plead sorry to those who advice me to post it to java people
because I have already done it.
Jus want to know alternatives to pointers which can be used with
C.While pointers provide flexibility most bugs are with respect to
pointers.So will it not be good if we are able to either forgo the
pointers or do some sort of modification(I am not aware how,but it can
be considered for research) so that our s/w s are more pure with out
bugs?

I am sorry for my amature query,but it will be helpful and I will be
thankful to all who makes me understand this.
Regards,
s.subbarayan

[Martin Ambuhl]

s.subbarayan wrote:

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?

Why in the world would anyone want to? Your question is similar to
asking "why don't people just cut off their left arms?".

[Case]

s.subbarayan wrote:

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows java
able to do this with out pointers?
I jus plead sorry to those who advice me to post it to java people
because I have already done it.
Jus want to know alternatives to pointers which can be used with
C.While pointers provide flexibility most bugs are with respect to
pointers.So will it not be good if we are able to either forgo the
pointers or do some sort of modification(I am not aware how,but it can
be considered for research) so that our s/w s are more pure with out
bugs?

I am sorry for my amature query,but it will be helpful and I will be
thankful to all who makes me understand this.

When you pass around objects in a Java program you're actually
passing around 'pointers' (references). In Java you don't write
the * and & as you would do in C because working with 'pointers'
has been built into the language.

I would argue that it is impossible to write well structured C
programs without using pointers. There are several applications
for pointers, which are hard/stupid to implement without:

a. Passing large chucks of data to functions (avoiding making
local copies.
b. Passing data to a function to be modified inside.
c. Various 'object-oriented' programming techniques using function
pointers.
d. Creating variable size data-structures like trees, lists, ...
e. ...

Perhaps we could say that imperative programming languages do well
with an abstract representation of a memory address (which 'is' a
pointer)? Well at least this might result in some interesting
responses. ;-)

Kees alias Case

[Leor Zolman]

On 21 May 2004 06:06:01 -0700, s_**********@re diffmail.com (s.subbarayan)
wrote:

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows java
able to do this with out pointers?
Java is an object-oriented language, and uses the "reference" type to refer
to objects. Primitive types are handled more-or-less the same way as they
are in C. Thus there's a dichotomy in Java: objects gets referred to only
via references (to facilitate performance and garbage collection), while
stand-alone ("naked") primitives are referred to directly by name, as in C,
for performance reasons (note there's no garbage collection for naked
primitives.). Primitives in Java rarely need to be accessed indirectly;
when they do, you in fact have to wrap them in an object and then use a
reference to that object.

C, on the other hand, has only one mechanism to refer to data indirectly,
and that's the pointer. It is the only game in town; it reflects well C's
nature of being "close to the machine", and allows the use of indirection
with or without dynamic allocation, and even with garbage collection if you
take the trouble to set up a custom framework for it. Pointers are the most
general-purpose way to do it, and provided the facilities necessary to make
C the first viable high-level (relatively speaking) systems programming
language. If you modified C to "remove pointers", it wouldn't be C any
longer. C++, for example, provides its own distinct flavor of reference
type, suitable for off-loading a number of things that, in C, have to be
done with pointers. But references aren't a universal replacement for
pointers even in C++.
I jus plead sorry to those who advice me to post it to java people
because I have already done it.
Jus want to know alternatives to pointers which can be used with
C.While pointers provide flexibility most bugs are with respect to
pointers.So will it not be good if we are able to either forgo the
pointers or do some sort of modification(I am not aware how,but it can
be considered for research) so that our s/w s are more pure with out
bugs?
The potential for pointer bugs is just the price you pay for the low-level
control C gives you. It is essentially a choice (made by /someone/, if not
you personally) regarding what language to use. If you need the greatest
possible "micro-management" of your application's behavior, you end up
using C. If you're willing to pay some price (in terms of either
performance, or learning curve struggles, or code size, or whatever), you
might choose to use a different language such as Java or C++ or Python or
something else.
-leor

I am sorry for my amature query,but it will be helpful and I will be
thankful to all who makes me understand this.
Regards,
s.subbarayan

--
Leor Zolman --- BD Software --- www.bdsoft.com
On-Site Training in C/C++, Java, Perl and Unix
C++ users: download BD Software's free STL Error Message Decryptor at:
www.bdsoft.com/tools/stlfilt.html

[Kurt Watzka]

s.subbarayan wrote:

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows java
able to do this with out pointers?
Java is not "able to do this without pointers". Anything derived from
Object _is_ represented as a pointer (under a different name) in Java.
If you follow a null reference, you get an exception in Java.
I jus plead sorry to those who advice me to post it to java people
because I have already done it.
Jus want to know alternatives to pointers which can be used with
C.
You could make _every_ object a pointer and get rid of the syntactic
differences between "pointer to user defined type" and "user defined
type" in a language similar to C. Just forbid storage class "auto"
for anything that is not a primitive built-in type.
While pointers provide flexibility most bugs are with respect to
pointers. So will it not be good if we are able to either forgo the
pointers or do some sort of modification(I am not aware how,but it can
be considered for research) so that our s/w s are more pure with out
bugs?

Forbid pointer arithmetic, add bounds checks to array access? Forbid the
use of types without a specifed (and matching) range as array indices?
Make free() take a pointer to the pointer to be disposed, and keep a
list of all pointer variables in your program so that free can set
the pointer _and all other pointer variables holding the same value_
to a trap representation? Forbid type casts on pointers?

While we are at it: Add explicit preconditions and postconditions
to functions. Add explicit conditions for validitiy to every user
defined type and make the language check those before and after every
use of an object of the user defined type. Make loop variants explicit.
Make loop invariants explicit.

And, last but not least: Change the name of the language. C is a language
that does not make you pay for things you don't need. If you need them,
you can implement them in C, and pay for them.

Kurt Watzka

[Malcolm]

"s.subbaray an" <s_**********@r ediffmail.com> wrote in message

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows > java able to do this with out pointers? All computer programs need to address memory (ie use pointers) internally. C
makes this fairly transparent to the user. Other languages hide the
underlying operation, at the cost of usually making code slower, but with
the advantage that it is less easy to access memory illegally.

You could try writing a "C--" (without pointers). When you try to write real
programs with it you will probably find that you need at the very least an
expandable array, and probably a "reference" scheme as well.

[Eric Sosman]

Malcolm wrote:

"s.subbaray an" <s_**********@r ediffmail.com> wrote in message

Dear all,
I had this following doubt,while java is able to carryon with out
pointers why C language cant be modified to remove pointer?Hows > java

able to do this with out pointers?

All computer programs need to address memory (ie use pointers) internally.

Off-topic nit: Alan Turing demonstrated that this is false.

--
Er*********@sun .com

[Martin Dickopp]

Eric Sosman <Er*********@su n.com> writes:

Malcolm wrote:

All computer programs need to address memory (ie use pointers)
internally.

Off-topic nit: Alan Turing demonstrated that this is false.

Even a Turing machine has a "pointer" as a part of its state: the
current tape position.

Martin
--
,--. Martin Dickopp, Dresden, Germany ,= ,-_-. =.
/ ,- ) http://www.zero-based.org/ ((_/)o o(\_))
\ `-' `-'(. .)`-'
`-. Debian, a variant of the GNU operating system. \_/

[August Derleth]

On Fri, 21 May 2004 18:51:57 +0100, Malcolm wrote:

You could try writing a "C--" (without pointers).

The name 'C--' is already in use: It's a language even lower-level than C
that is being touted as a compiler backend language.

http://www.cse.ogi.edu/PacSoft/projects/C--/

--
yvoregnevna gjragl-guerr gjb-gubhfnaq guerr ng lnubb qbg pbz
To email me, rot13 and convert spelled-out numbers to numeric form.
"Makes hackers smile" makes hackers smile.

[Michael Wojcik]

In article <cu************ *@zero-based.org>, Martin Dickopp <ex************ ****@zero-based.org> writes:

Eric Sosman <Er*********@su n.com> writes:

Malcolm wrote:

All computer programs need to address memory (ie use pointers)
internally.

Off-topic nit: Alan Turing demonstrated that this is false.

Even a Turing machine has a "pointer" as a part of its state: the
current tape position.

An n-PDA (n > 1) is equivalent to a TM. I don't see any pointer-
equivalent in an n-PDA.

Pointers aren't necessary. They're just very convenient. And to
answer the OP's question: if pointers were removed from C, it would
no longer be C.

--
Michael Wojcik mi************@ microfocus.com

HTML is as readable as C. You can take this either way. -- Charlie Gibbs