Reading unsigned values from string streams.

[BigMan]

Let's consider the following piece of code:

unsigned int ui;
std::istringstream StrStream( "-1" );
StrStream >> ui;

How do I catch the case when StrStream contains negative numbers?

 

[Mike Wahler]

Let's consider the following piece of code:

unsigned int ui;
std::istringstream StrStream( "-1" );
StrStream >> ui;

How do I catch the case when StrStream contains negative numbers?

Extract them and store them in a signed type object
(e.g. 'int' or 'long'), and check if less than zero.
(By definition, an unsigned object cannot represent
negative values). Because of the language's overflow
rules for unsigned types, (unsigned int)-1 == UINT_MAX.
(Overflow of signed types results in 'undefined behavior'.)

-Mike

 

[BigMan]

And how do I read values of pointer types?

 

[BigMan]

OK, let's suppose that I first read the value into an object of type
long. Then I'll have to make sure that this value fits in the signed
type. Is there a standard way to achieve this? May I use
std::numeric_limits::min and std::numeric_limits::max for this purpose?
And, by the way, does signed/unsigned comparison yield defined behavior?