equivalent class to POD

[cppquester]

I got an app where a bunch of values are set before the calculation is
fired up.

I need an elegant way to check if all variables have been set.
So for example for double I am thinking
about a

class Double
{
private;
double val;
bool init;

public:
Double(): init(false) {}
Double( double v): val( v), init( true) {}

double Get() { if( !init) throw "Error"; return val;}
};

For calculations I might have to define many operators.

Apart from that: Into which trouble am I running?
As I am probably not the first to think about this basic issue,
is there already an implemtation for the basic POD available?

Thanks,
Marc

[Scott Gifford]

cp********@goog lemail.com writes:

I got an app where a bunch of values are set before the calculation is
fired up.

I need an elegant way to check if all variables have been set.

Just some ideas to think about: When I need to do this, I often use a
pointer to that object, which can be NULL if it is unset, or a default
flag value that doesn't otherwise make sense in the application, for
example INT_MAX for an application that should use fairly small
integers, or nan() for an application that should use a float/double
but shouldn't accept "not a number" as valid. C will sometimes extend
the type of a return value to make room for extra information, for
example get() returns an int instead of an unsigned char, so that -1
can mean "end-of-file"; I can't think of similar examples in standard
C++, but it should still be a usable technique.

Another thought: Java and C# call standard data types with object
semantics (including being settable to NULL) "boxed types". That
might be a useful keyword to search for.

As far as I can see, the technique you propose should work, but sounds
tedious.

Hope this helps,

-----Scott.