string::size_type incrementation

Hi all,

I'm having problems with the following code:

Code:

std::string somestring;
std::string::size_type st;
st++ = somestring.rfind(' ');

I'm using g++ 4.0.3 and it gives me an error about, "invalid lvalue in assignment."

Obviously, I could modify the last line like this and just get along with it.

Code:

st = somestring.rfind(' ') + 1;

So I've learned for the first time that you cannot increment lvalues (if that's what's causing the problem).

So could somebody tell me why this restriction exists? Or at least throw me a link? Hopefully something more detailed than, "the standard says so."

At the moment, I really can't imagine of what use such a restriction might be.

I believe the result of the ++ operator is not a modifiable lvalue.

Stupid me. I always assumed the assignment operator had precedence over ++. Turns out its the other way around.

Clear as mud.