what are Rvalues and Lvalues in C++
[strong]on executing the below program i got error message like required Lvalue is missing in main function[/strong]
[strong] main() [/strong]
[strong]{[/strong]
[strong] int i;[/strong]
[strong] printf("%d",++i++); [/strong]
[strong]} [/strong]
[strong]plz tell me what are rvalues and lvalues. if there are any other values of this kind plz explain me that also[/strong]
Software/Hardware used:
Turbo c++/ visual c++
[strong] main() [/strong]
[strong]{[/strong]
[strong] int i;[/strong]
[strong] printf("%d",++i++); [/strong]
[strong]} [/strong]
[strong]plz tell me what are rvalues and lvalues. if there are any other values of this kind plz explain me that also[/strong]
Software/Hardware used:
Turbo c++/ visual c++
ASKED:
September 3, 2010 12:51 PM
UPDATED:
September 21, 2010 12:38 PM
Answer Wiki:
L-values are expressions that refer to memory locations, and are usually variables or objects. An l-value is something that could appear on the left side of an equal sign (i.e. something that you can assign a value to).
In your case, this part:
<pre>++i++</pre>
Is somehow equivalent to this:
<pre>i++ = (i++) + 1</pre>
But it is an ilegal expression, because you cannot assign a value to "i++". In other words, "i++" cannot appear on the left side of an equal sign, so it is not an l-value.
So, you can do this:
<pre>++i</pre>
or this:
<pre>i++</pre>
bot not this:
<pre>++i++</pre>
To see all answers submitted to the Answer Wiki: View Answer History.
i++ means to increment the variable after use
++i means to increment it before using
either way, as Carlosdl says, you cannot do both in a single command.
thank you for your reply sir,
I have one major doubt
is it correct to say that a l value is a super-set of r-value
“is it correct to say that a l value is a super-set of r-value”
I don’t think so.
Rather, I would say that r-values are a superset of l-values, because all l-values are r-values, but not vice versa.
ya right now I got it,
(up to my knowledge)
r-values are values that are on the right hand side and they can be a variable (pointing a location in memory) or it can be just a value(a number or character)
but only a variable pointing to the memory location can be a l-value
thank you sir, for your kind reply