[DM-dev] basic_istream

[Stephan B. <st...@wa...>]

Good afternoon, all,

Looking at the basic_istream STL class, I think this will be a better 
replacement for all FILE operations we do. For one, we could overload the << 
and >> operators, so we could do something like this:

DungeonElement *de = 0;
mystream >> de; // parses out x,y,w,h, etc.

This would also allow us to use the same code for console and file i/o, by 
simply using different streams. You could even then do:

cout << "enter dungeon item parameters (x,y,w,h): ";
cinn >> de;
if( de->isValid() )... // assume it sets a 'valid' flag if this works, since 
we can't (or shouldn't, actually, per Scott Meyers) return values in the 
normal sense from an operator overload.

See:
http://stephan.rootonfire.org/.cpp/istream.html#basic_iostream

Overloading operators sounds hard, but it's not. Here's an overloaded 
operator from QUB:
declaration:
 friend ostream & operator << (ostream&, const GCom &); 
implementation:
operator<<(ostream &os, const GCom &gc)
{
    os << gc.toString().data();
    return os;
}


Some text from the docs:
The functions:basic_istream& operator>>(short& val);
basic_istream& operator>>(unsigned short& val);
basic_istream& operator>>(int& val);
basic_istream& operator>>(unsigned int& val);
basic_istream& operator>>(long& val);
basic_istream& operator>>(unsigned long& val);
basic_istream& operator>>(void *& val);

each extract a field and convert it to a numeric value by calling 
use_facet<num_get<Elem, InIt>(getloc()). get(InIt( rdbuf()), Init(0), *this, 
getloc(), val). Here, InIt is defined as istreambuf_iterator<Elem, Tr>, and 
val has type long, unsigned long, or void * as needed.

Geez, they don't make these things simple to read. The top part, fine, but:
use_facet<num_get<Elem, InIt>(getloc()). get(InIt( rdbuf()), Init(0), *this, 
getloc(), val)

Actually... that text is incorrect. They left out a > somewhere. Ah, well, I 
can't make any sense out of multiply-nested template stuff, anyway. It 
confuses me. If you think about it, to subclass a template class it to have a 
child of something which doesn't exist until the child does.


Unrelated: I've added <string.h> to DungeonMaker.cpp in the new tree so it'll 
build on Mandrake. On my system this is taken care of by <string>, it appears.

----- Stephan Beal - st...@wa...
http://qub.sourceforge.net - http://gwm.rootonfire.org
http://byoo.rootonfire.org - http://dungeonmaker.sourceforge.net
"Now I'm not normally the kind of person who likes to trespass, but
sometimes you just find yourself over the line." -- Bob Dylan