Increment / Decrement Operators - Help

Hi All,


I have an small doubt in using Increment / Decrement operators....

Program is :

Code:

---

1)  #include<stdio.h>
2)  main()
3)  {
4)    int i=10;
5)    printf("\nValue of I is :%d",++(--i));
6)    getch();
7)  }

---

Compilation Error:
at line 5, Error prompting stating "L value required".

Is the syntax wrong or the usage of the Increment / Decrement operators is worng....

Best Regards,
Shyamlal SVS.

The usage is wrong, incrementing and decrementing returns an R value.

Since the incrementing and recrementing are implemented as single assembly instructions(inc/dec), you cannot use them at the same time. Also, ++(i-2) will not work!

See the assembly output of an increment statement.

Code:

---

        movl    $10, -4(%ebp) <-- i=10
        leal    -4(%ebp), %eax
        incl    (%eax)  <-- here is the i++

---

Code:

---

The usage is wrong, incrementing and decrementing returns an R value.

---

Cud u explain me what is R value?????

Quote:

---

Originally Posted by shyam168

Cud u explain me what is R value?????

---

L-values are values that have addresses, meaning they are variables or dereferenced references to a certain place.
R-value is either l-value or non-l-value — a term only used to distinguish from l-value.

An l-value is a value that can be used on the left side of an assigment operator. An r-value is a value that can be used on the right side of an assignment operator:

Code:

---

l-value = r-value;

---

Code:

---

++(--i)

---

The expression highlighted in red yields the value 9. Obviously, this can not be used as as an l-value.

The ++ operator, highlighted in blue, requires an l-value because it assigns a value to the value it is used on. Trying to use it on the value 9 would look like this:

Code:

---

/* 9 is not an l-value. This code won't work. */
9 = 9 + 1;

---

Thanks to one and all forn clearing my doubt.....

:) :)