Question

Describe r-value and l-value. Can a r-value be a l-value? Can a l-value be a r-value? Use examples.

Answer 1

r-value:

r-value is an expression that is stored at some memory location and it can't have a value assigned to it.

This can be on the right-hand side of the assignment operator but not on the left-hand side of the assignment operator.

For example:

int a, b;

b = 10;

a = b + 5;

Here in the third statement, the expression 'b+5' is an r-value.

l-value:

l-value is an object that refers to some memory location and it can have a value assigned to it.

This can be on the left-hand side or right-hand side of the assignment operator.

For example:

int a, b;

a = 10;

Here in the second statement, 'a' is an l-value.

b = a;

In the above statement, 'l-value' appearing on right-hand side fo the assignment operator.

Can an r-value be a l-value?

No, because an r-value is an expression and an expression is not allowed in the left-hand side of the assignment operator.

For example:

int a;

10 = a; //Not allowed

Can a l-value be an r-value?

Yes, l-value is an object that refers to some memory location and it can have a value assigned to it.

For example:

For example:

int c, d;

c = 20;

Here in the second statement, 'c' is an l-value.

d = c;

In the above statement, 'l-value' appearing on right-hand side fo the assignment operator.