lvalue error needs explanation

[Akhil]

plz c d following code

#include<stdio. h>
void main()
{
int x=4,y=1;

y=x++++; //gives error message lvalue required

y=x++ + ++y;//no errors

y=x+++++y ;//lvalue required

y=(++x)++; //no errors
}

explanation needed for the all four statements nd a bit bout lvalues.

program tested on turbo 4.5 32 bit compiler.

[Chris Dollin]

Akhil wrote:

plz c d following code
Syntax error: non-word "plz".
Syntax error: unexpected initial "c".
Syntax error: unexpected initial "d".
Syntax error: imperative must end with "." or "!".
Warning: April is the cruelest month.
#include<stdio. h>
void main()
non-int `main`s produce undefined behaviour.
{
int x=4,y=1;

y=x++++; //gives error message lvalue required
An "lvalue" is (roughly) an addressable object, a variable.
The left operand of ++ must be a lvalue. The result of ++
is a number. Numbers are not lvalues. QED.
program tested on turbo 4.5 32 bit compiler.

If it were a program, it would have compiled.

--
Chris "try, or try not -- there is no do" Dollin

[Akhil]

thnx for d reply but i still hav a problem ....

if we exeucte the statement y=(++x)++; then thr is no error ++x will
again b a number nd left operand of ++ shud b a lvalue so y does it
work in this case.

[Chris Dollin]

Akhil wrote:

thnx for d reply but i still hav a problem ....
Yes, you're still writing in gobbledegook. Please use English words
and English grammar.
if we exeucte the statement y=(++x)++; then thr is no error
Yes, there is - "invalid lvalue in increment" is how my local gcc reported
it.
++x will
again b a number nd left operand of ++ shud b a lvalue so y does it
work in this case.

Broken compiler - /if/ it really did work.

--
Chris "try, or try not -- there is no do" Dollin

[CBFalconer]

Akhil wrote:

plz c d following code
Gobble-de-gook is not understandable.

#include<stdio. h>
void main()
main returns int. All bets are off.
{
int x=4,y=1;

y=x++++; //gives error message lvalue required
Syntax errors normally do that.

.... snip ...
program tested on turbo 4.5 32 bit compiler.

No non-compilable program is tested.

--
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[Ian Collins]

Akhil wrote:

plz c d following code

#include<stdio. h>
void main()
{
int x=4,y=1;

y=x++++; //gives error message lvalue required

You can't modify the result of x++, so it can't be an lvalue (something
that appears on the left hand side of an expression).
--
Ian Collins.

[Ian Collins]

Ian Collins wrote:

Akhil wrote:

plz c d following code

#include<stdio. h>
void main()
{
int x=4,y=1;

y=x++++; //gives error message lvalue required

You can't modify the result of x++, so it can't be an lvalue (something
that appears on the left hand side of an expression).

Sorry, that came out wrong, I should have said you can't modify the
expression x++.

--
Ian Collins.

[Jordan Abel]

On 2006-02-08, Akhil <ak************ *@gmail.com> wrote:

plz c d following code

#include<stdio. h>
void main()
{
int x=4,y=1;

y=x++++; //gives error message lvalue required
x++ returns a value, which you are then trying to increment
y=x++ + ++y;//no errors
Except, of course, the undefined behavior
y=x+++++y ;//lvalue required
this parses as x++ ++ +y
y=(++x)++; //no errors
It _should_ be the same error as x++++ - i can't imagine why it's not.
Have you actually tried this, or did your teacher just _say_ there are
no errors?
} explanation needed for the all four statements nd a bit bout lvalues.
lvalues are, basically, expressions that it is legal to assign to /
modify / increment - say, the name of a variable.
program tested on turbo 4.5 32 bit compiler.

[Jordan Abel]

On 2006-02-08, Akhil <ak************ *@gmail.com> wrote:

thnx for d reply but i still hav a problem ....

if we exeucte the statement y=(++x)++; then thr is no error ++x will
again b a number nd left operand of ++ shud b a lvalue so y does it
work in this case.

Your compiler failed to provide a required diagnostic, and is thus not a
conforming ANSI C implementation.

[Vladimir S. Oka]

Jordan Abel wrote:

On 2006-02-08, Akhil <ak************ *@gmail.com> wrote:

y=(++x)++; //no errors

It _should_ be the same error as x++++ - i can't imagine why it's not.
Have you actually tried this, or did your teacher just _say_ there are
no errors?

It certainly produces the same `lvalue` error on GCC 3.4.2
(mingw-special) when compiled with paranoid options.

program tested on turbo 4.5 32 bit compiler.

Don't have this to test OP's results, but I have a strogn suspicion
that OP did not in fact try to compile this. If it does really compile
on TC 4.5, I'd complain to the vendor, but that won't work, as it's
discontinued.

--
BR, Vladimir